View source for Metadata

{{short description|Data about data}}
[[File:Schlagwortkatalog.jpg|thumb|In the 21st century, metadata typically refers to digital forms, but traditional card catalogs contain metadata, with cards holding [[Information|information]] about books in a library (author, title, subject, etc.).]]
[[File:Cenchrus ciliaris L. 438045083.jpg|thumb|Metadata can come in different layers: This physical [[Biology:Herbarium|herbarium]] record of ''Cenchrus ciliaris'' consists of the specimens as well as metadata about them, while the barcode points to a digital record with metadata about the physical record.]]
[[File:Sphagnum papillosum at Sphagnum cultivation at Universität Greifswald 2023-06-11 01.jpg|thumb|Metadata for a ''[[Biology:Sphagnum papillosum|Sphagnum papillosum]]'' pot that is part of a common garden experiment at Universität Greifswald]]

'''Metadata''' (or '''metainformation''') is "[[Data|data]] that provides information about other data",<ref>{{cite web |url=http://www.merriam-webster.com/dictionary/metadata |title=Merriam Webster |access-date=17 October 2019 |url-status=live |archive-url=https://web.archive.org/web/20150227084709/http://www.merriam-webster.com/dictionary/metadata |archive-date=27 February 2015}}</ref> but not the content of the data itself, such as the text of a message or the image itself.<ref name="Gonzalez-Perez (2018)">{{cite book |vauthors=Gonzalez-Perez C |date=2018 |title=Information modelling for archaeology and anthropology: software engineering principles for cultural heritage |chapter=Metainformation |pages=181–189 |veditors=Gonzalez-Perez C |edition=1st |publisher=Springer Cham |isbn=978-3-319-72652-6}}</ref> There are many distinct types of metadata, including:
* '''Descriptive metadata''' – the descriptive information about a resource. It is used for discovery and identification. It includes elements such as title, abstract, author, and keywords.
* '''Structural metadata''' – metadata about containers of data and indicates how compound objects are put together, for example, how pages are ordered to form chapters. It describes the types, versions, relationships, and other characteristics of digital materials.<ref>{{cite web |url=http://www.dlib.org/dlib/february97/cnri/02arms1.html |title=An Architecture for Information in Digital Libraries |access-date=10 May 2017 |url-status=live |archive-url=https://web.archive.org/web/20170327015501/http://www.dlib.org/dlib/february97/cnri/02arms1.html |archive-date=27 March 2017}}</ref>
* '''Administrative metadata'''<ref name="Metadata Basics Outline">{{cite web |url=http://marciazeng.slis.kent.edu/metadatabasics/types.htm |title=Metadata Types and Functions |publisher=NISO |date=2004 |access-date=5 October 2016 |author=Zeng, Marcia |url-status=live |archive-url=https://web.archive.org/web/20161007120833/http://marciazeng.slis.kent.edu/metadatabasics/types.htm |archive-date=7 October 2016}}</ref> – the information to help manage a resource, like resource type, permissions, and when and how it was created.<ref name="Understanding Metadata (2)">{{cite book |url=http://www.niso.org/publications/press/UnderstandingMetadata.pdf |title=Understanding Metadata |publisher=NISO Press |author=National Information Standards Organization (NISO) |year=2001 |isbn=978-1-880124-62-8 |page=1 |url-status=dead |archive-url=https://web.archive.org/web/20141107022958/http://www.niso.org/publications/press/UnderstandingMetadata.pdf |archive-date=7 November 2014 |access-date=20 June 2008}}</ref>
* '''Reference metadata''' – the information about the contents and quality of [[Statistical data type|statistical data]].
* '''Statistical metadata'''<ref name=":4">{{Cite web |url=https://stats.oecd.org/glossary/detail.asp?ID=7076 |title=OECD Glossary of Statistical Terms – Reference metadata Definition |last=Directorate |first=OECD Statistics |website=stats.oecd.org |access-date=24 May 2018 |archive-date=11 July 2021 |archive-url=https://web.archive.org/web/20210711201158/https://stats.oecd.org/glossary/detail.asp?ID=7076 |url-status=live}}</ref> – also called process data, may describe processes that collect, process, or produce statistical data.<ref name=":5">{{Cite web |url=https://www.bls.gov/osmr/research-papers/2000/pdf/st000040.pdf |title=The Role of Metadata in Statistics |last1=Dippo |first1=Cathryn |last2=Sundgren |first2=Bo |website=Bureau of Labor Statistics |access-date=3 February 2021 |archive-date=14 July 2021 |archive-url=https://web.archive.org/web/20210714090220/https://www.bls.gov/osmr/research-papers/2000/pdf/st000040.pdf |url-status=live}}</ref>
* '''Legal metadata''' – provides information about the creator, [[Copyright|copyright]] holder, and public licensing, if provided.

Metadata is not strictly bound to one of these categories, as it can describe a piece of data in many other ways.

== History ==
Metadata has various purposes. It can help users [[Findability|find relevant information]] and [[Discoverability|discover resources]]. It can also help organize electronic resources, provide digital identification, and archive and preserve resources. Metadata allows users to access resources by "allowing resources to be found by relevant criteria, identifying resources, bringing similar resources together, distinguishing dissimilar resources, and giving location information".<ref name="Understanding_Metadata" /> Metadata of telecommunication activities including [[Internet]] traffic is very widely collected by various national governmental organizations. This data is used for the purposes of [[Traffic analysis|traffic analysis]] and can be used for mass surveillance.<ref>{{cite web |url=https://www.schneier.com/essays/archives/2014/03/metadata_surveillanc.html |title=Metadata = Surveillance |access-date=6 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160621225840/https://www.schneier.com/essays/archives/2014/03/metadata_surveillanc.html |archive-date=21 June 2016}}</ref>

Metadata was traditionally used in the [[Library catalog|card catalogs]] of libraries until the 1980s when libraries converted their catalog data to digital [[Database|database]]s.<ref>{{Cite book |last1=Holly |first1=Yu |url=https://books.google.com/books?id=aZGyjL3uatIC&pg=PA4 |title=Electronic Resource Management in Libraries: Research and Practice: Research and Practice |last2=Scott |first2=Breivold |date=28 February 2008 |publisher=IGI Global |isbn=978-1-59904-892-5 |pages=4 |language=en |access-date=26 November 2022 |archive-date=26 November 2022 |archive-url=https://web.archive.org/web/20221126135426/https://books.google.com/books?id=aZGyjL3uatIC&pg=PA4 |url-status=live}}</ref> In the 2000s, as data and information were increasingly stored digitally, this digital data was described using metadata standards.<ref>{{Cite book |last1=Tedd |first1=Lucy A. |url=https://books.google.com/books?id=u_Gi1CPuP3kC&pg=PA90 |title=Digital Libraries: Principles and Practice in a Global Environment |last2=Large |first2=J. Andrew |date=4 April 2005 |publisher=Walter de Gruyter |isbn=978-3-598-44005-2 |pages=90 |language=en |access-date=26 November 2022 |archive-date=26 November 2022 |archive-url=https://web.archive.org/web/20221126140825/https://books.google.com/books?id=u_Gi1CPuP3kC&pg=PA90 |url-status=live}}</ref>

The first description of "meta data" for computer systems is purportedly noted by MIT's Center for International Studies experts David Griffel and Stuart McIntosh in 1967: "In summary then, we have statements in an object language about subject descriptions of data and token codes for the data. We also have statements in a meta language describing the data relationships and transformations, and ought/is relations between norm and data."<ref>{{Cite journal |last=Steiner |first=Tobias |date=23 November 2017 |title=Metadaten und OER: Geschichte einer Beziehung (Metadata and OER: [hi]story of a relationship) |journal=Synergie. Fachmagazin für Digitalisierung in der Lehre |language=de-DE |volume=04 |doi=10.17613/m6p81g |issn=2509-3096 |page=54}}</ref>

Unique metadata standards exist for different disciplines (e.g., [[Social:Museum|museum]] collections, digital audio files, websites, etc.). Describing the contents and [[Context (computing)|context]] of data or [[Computer file|data files]] increases its usefulness. For example, a [[HTML editor|web page]] may include metadata specifying what software language the page is written in (e.g., HTML), what tools were used to create it, what subjects the page is about, and where to find more information about the subject. This metadata can automatically improve the reader's experience and make it easier for users to find the web page online.<ref name="Practices in Using Metadata">{{cite web |url=http://www.library.illinois.edu/dcc/bestpractices/chapter_11_structuralmetadata.html |title=Best Practices for Structural Metadata |publisher=University of Illinois |date=15 December 2010 |access-date=17 June 2016 |url-status=live |archive-url=https://web.archive.org/web/20160624011712/http://www.library.illinois.edu/dcc/bestpractices/chapter_11_structuralmetadata.html |archive-date=24 June 2016}}</ref> A [[Engineering:CD|CD]] may include metadata providing information about the musicians, singers, and songwriters whose work appears on the disc.

In many countries, government organizations routinely store metadata about emails, telephone calls, web pages, video traffic, IP connections, and cell phone locations.{{Citation needed|date=November 2023}}

== Definition ==
Metadata means "data about data". Metadata is defined as the data providing information about one or more aspects of the data; it is used to summarize basic information about data that can make tracking and working with specific data easier.<ref>{{cite web |title=A Guardian Guide to your Metadata |website=theguardian.com | publisher=Guardian News and Media Limited | date=12 June 2013 |url=https://www.theguardian.com/technology/interactive/2013/jun/12/what-is-metadata-nsa-surveillance#meta=0000000 |url-status=live |archive-url=https://web.archive.org/web/20160306145239/http://www.theguardian.com/technology/interactive/2013/jun/12/what-is-metadata-nsa-surveillance#meta=0000000 |archive-date=6 March 2016}}</ref> Some examples include:
* Means of creation of the data
* Purpose of the data
* Time and date of creation
* Creator or author of the data
* Location on a [[Computer network|computer network]] where the data was created
* [[Technical standard|Standards]] used
* File size
* Data quality
* Source of the data
* Process used to create the data

For example, a [[Digital image|digital image]] may include metadata that describes the size of the image, its color depth, resolution, when it was created, the shutter speed, and other data.<ref>{{cite web |url=http://www.adeoimaging.com/ |title=ADEO Imaging: TIFF Metadata |access-date=20 May 2013 |url-status=live |archive-url=https://web.archive.org/web/20130517055358/http://www.adeoimaging.com/ |archive-date=17 May 2013}}</ref> A text document's metadata may contain information about how long the document is, who the author is, when the document was written, and a short summary of the document. Metadata within web pages can also contain descriptions of page content, as well as key words linked to the content.<ref name="Rouse, M (2014)">{{cite web |last=Rouse |first=Margaret |title=Metadata |work=WhatIs |publisher=TechTarget |date=July 2014 |url=http://whatis.techtarget.com/definition/metadata |url-status=live |archive-url=https://web.archive.org/web/20151029154730/http://whatis.techtarget.com/definition/metadata |archive-date=29 October 2015}}</ref> These links are often called "Metatags", which were used as the primary factor in determining order for a web search until the late 1990s.<ref name="Rouse, M (2014)" /> The reliance on metatags in web searches was decreased in the late 1990s because of "keyword stuffing",<ref name="Rouse, M (2014)" /> whereby metatags were being largely misused to trick search engines into thinking some websites had more relevance in the search than they really did.<ref name="Rouse, M (2014)" />

Metadata can be stored and managed in a [[Database|database]], often called a [[Metadata registry|metadata registry]] or [[Metadata repository|metadata repository]].<ref>Hüner, K.; Otto, B.; Österle, H.: Collaborative management of business metadata, in: ''International Journal of Information Management'', 2011</ref> However, without context and a point of reference, it might be impossible to identify metadata just by looking at it.<ref>{{cite web |url=http://www.bls.gov/ore/pdf/st000010.pdf |title=Metadata Standards And Metadata Registries: An Overview |access-date=23 December 2011 |url-status=live |archive-url=https://web.archive.org/web/20110629082434/http://www.bls.gov/ore/pdf/st000010.pdf |archive-date=29 June 2011}}</ref> For example: by itself, a database containing several numbers, all 13 digits long could be the results of calculations or a list of numbers to plug into an {{nowrap|equation{{hsp}}{{snd}}}}{{hsp}}without any other context, the numbers themselves can be perceived as the data. But if given the context that this database is a log of a book collection, those 13-digit numbers may now be identified as {{nowrap|[[ISBN]]s{{hsp}}{{snd}}}}{{hsp}}information that refers to the book, but is not itself the information within the book. The term "metadata" was coined in 1968 by Philip Bagley, in his book "Extension of Programming Language Concepts" where it is clear that he uses the term in the ISO 11179 "traditional" sense, which is "structural metadata" i.e. "data about the containers of data"; rather than the alternative sense "content about individual instances of data content" or metacontent, the type of data usually found in library catalogs.<ref name="Bagley">{{Cite web |first=Philip |last=Bagley |title=Extension of programming language concepts |date=November 1968 |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/680815.pdf |publisher=University City Science Center |location=Philadelphia |url-status=live |archive-url=https://web.archive.org/web/20121130091053/http://www.dtic.mil/dtic/tr/fulltext/u2/680815.pdf |archive-date=30 November 2012}}</ref><ref>"The notion of "metadata" introduced by Bagley". {{Cite news |last1=Solntseff |first1=N+1 |last2=Yezerski |first2=A |year=1974 |title=A survey of extensible programming languages |series=Annual Review in Automatic Programming |publisher=Elsevier Science Ltd |volume=7 |pages=267–307 |doi=10.1016/0066-4138(74)90001-9}}</ref> Since then the fields of information management, information science, information technology, librarianship, and GIS have widely adopted the term. In these fields, the word ''metadata'' is defined as "data about data".<ref name="NISO">{{Cite book |last=NISO |title=Understanding Metadata |publisher=NISO Press |url=http://www.niso.org/publications/press/UnderstandingMetadata.pdf |isbn=978-1-880124-62-8 |access-date=5 January 2010 |url-status=dead |archive-url=https://web.archive.org/web/20141107022958/http://www.niso.org/publications/press/UnderstandingMetadata.pdf |archive-date=7 November 2014 |year=2004 |page=1}}</ref> While this is the generally accepted definition, various disciplines have adopted their own more specific explanations and uses of the term.

''Slate'' reported in 2013 that the United States government's interpretation of "metadata" could be broad, and might include message content such as the subject lines of emails.<ref>{{Cite web |url=https://slate.com/technology/2013/11/dni-patriot-act-section-215-documents-show-how-government-inflated-metadata-definition.html |title=Newly Released Documents Show How Government Inflated the Definition of Metadata |first=Josephine |last=Wolff |date=20 November 2013 |website=Slate Magazine |access-date=12 June 2021 |archive-date=15 June 2021 |archive-url=https://web.archive.org/web/20210615151742/https://slate.com/technology/2013/11/dni-patriot-act-section-215-documents-show-how-government-inflated-metadata-definition.html |url-status=live}}</ref>

== Types ==
While the metadata application is manifold, covering a large variety of fields, there are specialized and well-accepted models to specify types of metadata. [[Biography:Francis Bretherton|Bretherton]] & Singley (1994) distinguish between two distinct classes: structural/control metadata and guide metadata.<ref>{{Cite conference |first1=F. P. |last1=Bretherton |first2=P.T. |last2=Singley |title=Metadata: A User's View, Proceedings of the International Conference on Very Large Data Bases (VLDB) |pages=1091–1094 |year=1994}}</ref> ''Structural metadata'' describes the structure of database objects such as tables, columns, keys and indexes. ''Guide metadata'' helps humans find specific items and is usually expressed as a set of keywords in a natural language. According to Ralph Kimball, metadata can be divided into three categories: ''technical metadata'' (or internal metadata), ''[[Business metadata|business metadata]]'' (or external metadata), and ''process metadata''.

NISO distinguishes three types of metadata: descriptive, structural, and administrative.<ref name="NISO" /> ''Descriptive metadata'' is typically used for discovery and identification, as information to search and locate an object, such as title, authors, subjects, keywords, and publisher. ''Structural metadata'' describes how the components of an object are organized. An example of structural metadata would be how pages are ordered to form chapters of a book. Finally, ''administrative metadata'' gives information to help manage the source. Administrative metadata refers to the technical information, such as file type, or when and how the file was created. Two sub-types of administrative metadata are rights management metadata and preservation metadata. ''Rights management metadata'' explains intellectual property rights, while ''preservation metadata'' contains information to preserve and save a resource.<ref name="Understanding_Metadata">{{cite book |last=National Information Standards Organization |title=Understanding Metadata |year=2004 |publisher=NISO Press |location=Bethesda, MD |isbn=978-1-880124-62-8 |url=http://www.niso.org/publications/press/UnderstandingMetadata.pdf |author2=Rebecca Guenther |author3=Jaqueline Radebaugh |access-date=13 July 2022 |page=15 |archive-url=https://web.archive.org/web/20141107022958/http://www.niso.org/publications/press/UnderstandingMetadata.pdf |archive-date=7 November 2014}}</ref>

Statistical data repositories have their own requirements for metadata in order to describe not only the source and quality of the data<ref name=":4" /> but also what statistical processes were used to create the data, which is of particular importance to the statistical community in order to both validate and improve the process of statistical data production.<ref name=":5" />

An additional type of metadata beginning to be more developed is ''accessibility metadata''. Accessibility metadata is not a new concept to libraries; however, advances in universal design have raised its profile.<ref name="Beyene (2017)">{{cite journal |last1=Beyene |first1=Wondwossen Mulualem |title=Metadata and universal access in digital library environments |journal=Library Hi Tech |date=2017 |volume=35 |issue=2 |pages=210–221 |doi=10.1108/LHT-06-2016-0074 |hdl=10642/5994 |hdl-access=free}}</ref>{{rp|213–214}} Projects like Cloud4All and GPII identified the lack of common terminologies and models to describe the needs and preferences of users and information that fits those needs as a major gap in providing universal access solutions.<ref name="Beyene (2017)" />{{rp|210–211}} Those types of information are accessibility metadata.<ref name="Beyene (2017)" />{{rp|214}} [http://schema.org/ Schema.org] has incorporated several accessibility properties based on IMS Global Access for All Information Model Data Element Specification.<ref name="Beyene (2017)" />{{rp|214}} The Wiki page [https://www.w3.org/wiki/WebSchemas/Accessibility WebSchemas/Accessibility] lists several properties and their values.  While the efforts to describe and standardize the varied accessibility needs of information seekers are beginning to become more robust, their adoption into established metadata schemas has not been as developed. For example, while Dublin Core (DC)'s "audience" and MARC 21's "reading level" could be used to identify resources suitable for users with dyslexia and DC's "format" could be used to identify resources available in braille, audio, or large print formats, there is more work to be done.<ref name="Beyene (2017)" />{{rp|214}}

== Structures ==
Metadata (metacontent) or, more correctly, the vocabularies used to assemble metadata (metacontent) statements, is typically structured according to a standardized concept using a well-defined metadata scheme, including metadata standards and [[Metadata modeling|metadata models]]. Tools such as [[Controlled vocabulary|controlled vocabularies]], [[Taxonomy (general)|taxonomies]], [[Thesaurus (information retrieval)|thesauri]], data dictionaries, and [[Metadata registry|metadata registries]] can be used to apply further standardization to the metadata. Structural metadata commonality is also of paramount importance in [[Data model|data model]] development and in [[Database design|database design]].

=== Syntax ===
Metadata (metacontent) syntax refers to the rules created to structure the fields or elements of metadata (metacontent).<ref>{{cite web |url=http://www.nla.gov.au/nla/staffpaper/cathro3.html |title=Metadata: an overview |last=Cathro |first=Warwick |year=1997 |archive-url=https://web.archive.org/web/20091222232625/http://www.nla.gov.au/nla/staffpaper/cathro3.html |archive-date=22 December 2009 |url-status=live |access-date=6 January 2010}}</ref> A single metadata scheme may be expressed in a number of different markup or programming languages, each of which requires a different syntax. For example, Dublin Core may be expressed in plain text, [[HTML]], [[XML]], and [[Resource Description Framework|RDF]].<ref>{{cite web |last=DCMI |author-link=Dublin Core Metadata Initiative |title=Semantic Recommendations |date=5 October 2009 |url=http://dublincore.org/specifications/ |access-date=6 January 2010 |url-status=live |archive-url=https://web.archive.org/web/20091231035647/http://dublincore.org/specifications/ |archive-date=31 December 2009}}</ref>

A common example of (guide) metacontent is the bibliographic classification, the subject, the [[List of Dewey Decimal classes|Dewey Decimal class number]]. There is always an implied statement in any "classification" of some object. To classify an object as, for example, Dewey class number 514 (Topology) (i.e. books having the number 514 on their spine) the implied statement is: "<nowiki><book><subject heading><514></nowiki>". This is a subject-predicate-object triple, or more importantly, a class-attribute-value triple. The first 2 elements of the triple (class, attribute) are pieces of some structural metadata having a defined semantic. The third element is a value, preferably from some controlled vocabulary, some reference (master) data. The combination of the metadata and master data elements results in a statement which is a metacontent statement i.e. "metacontent = metadata + master data". All of these elements can be thought of as "vocabulary". Both metadata and master data are vocabularies that can be assembled into metacontent statements. There are many sources of these vocabularies, both meta and master data: UML, EDIFACT, XSD, Dewey/UDC/LoC, SKOS, ISO-25964, Pantone, Linnaean Binomial Nomenclature, etc. Using controlled vocabularies for the components of metacontent statements, whether for indexing or finding, is endorsed by [[ISO 25964]]: "If both the indexer and the searcher are guided to choose the same term for the same concept, then relevant documents will be retrieved."<ref>{{cite web |url=https://www.iso.org/obp/ui/#iso:std:iso:25964:-1:ed-1:v1:en |title=ISO 25964-1:2011(en) |publisher=ISO.org |archive-url=https://web.archive.org/web/20160617031837/https://www.iso.org/obp/ui/ |archive-date=17 June 2016}}</ref> This is particularly relevant when considering search engines of the internet, such as Google. The process indexes pages and then matches text strings using its complex algorithm; there is no intelligence or "inferencing" occurring, just the illusion thereof.

=== Hierarchical, linear, and planar schemata ===
Metadata schemata can be hierarchical in nature where relationships exist between metadata elements and elements are nested so that parent-child relationships exist between the elements.
An example of a hierarchical metadata schema is the [[Learning object metadata|IEEE LOM]] schema, in which metadata elements may belong to a parent metadata element.
Metadata schemata can also be one-dimensional, or linear, where each element is completely discrete from other elements and classified according to one dimension only.
An example of a linear metadata schema is the Dublin Core schema, which is one-dimensional.
Metadata schemata are often 2 dimensional, or planar, where each element is completely discrete from other elements but classified according to 2 orthogonal dimensions.<ref>{{cite web |title=Types of Metadata |publisher=University of Melbourne | date=15 August 2006 |url=http://www.infodiv.unimelb.edu.au/metadata/add_info.html |access-date=6 January 2010 |archive-url=https://web.archive.org/web/20091024112353/http://www.infodiv.unimelb.edu.au/metadata/add_info.html |archive-date=24 October 2009}}</ref>

=== Granularity ===
The degree to which the data or metadata is structured is referred to as "granularity". "Granularity" refers to how much detail is provided. Metadata with a high granularity allows for deeper, more detailed, and more structured information and enables a greater level of technical manipulation. A lower level of granularity means that metadata can be created for considerably lower costs but will not provide as detailed information. The major impact of granularity is not only on creation and capture, but moreover on maintenance costs. As soon as the metadata structures become outdated, so too is the access to the referred data. Hence granularity must take into account the effort to create the metadata as well as the effort to maintain it.

=== Hypermapping ===
In all cases where the metadata schemata exceed the planar depiction, some type of hypermapping is required to enable display and view of metadata according to chosen aspect and to serve special views. Hypermapping frequently applies to layering of geographical and geological information overlays.<ref>{{cite web |url=http://www.isprs.org/proceedings/XXXII/part4/kuebler51.pdf |title=The Design and Development of a Geologic Hypermap Prototype |first1=Stefanie |last1=Kübler |first2=Wolfdietrich |last2=Skala |first3=Agnès |last3=Voisard |url-status=live |archive-url=https://web.archive.org/web/20131003182157/http://www.isprs.org/proceedings/XXXII/part4/kuebler51.pdf |archive-date=3 October 2013}}</ref>

== Standards ==
International standards apply to metadata. Much work is being accomplished in the national and international standards communities, especially ANSI (American National Standards Institute) and [[Organization:International Organization for Standardization|ISO]] (International Organization for Standardization) to reach a consensus on standardizing metadata and registries. The core metadata registry standard is [[Organization:International Organization for Standardization|ISO]]/[[Organization:International Electrotechnical Commission|IEC]] 11179 Metadata Registries (MDR), the framework for the standard is described in ISO/IEC 11179-1:2004.<ref>{{cite web |url=http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39438 |title=ISO/IEC 11179-1:2004 Information technology – Metadata registries (MDR) – Part 1: Framework |publisher=Iso.org |date=18 March 2009 |access-date=23 December 2011 |url-status=live |archive-url=https://web.archive.org/web/20120117154947/http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=39438 |archive-date=17 January 2012}}</ref> A new edition of Part 1 is in its final stage for publication in 2015 or early 2016. It has been revised to align with the current edition of Part 3, ISO/IEC 11179-3:2013<ref>{{cite web |url=http://standards.iso.org/ittf/PubliclyAvailableStandards/c050340_ISO_IEC_11179-3_2013.zip |title=ISO/IEC 11179-3:2013 Information technology-Metadata registries – Part 3: Registry metamodel and basic attributes |publisher=International Organization for Standardization |date=2014 |access-date=23 August 2015 |archive-date=5 July 2017 |archive-url=https://web.archive.org/web/20170705111711/http://standards.iso.org/ittf/PubliclyAvailableStandards/c050340_ISO_IEC_11179-3_2013.zip |url-status=live}}</ref> which extends the MDR to support the registration of Concept Systems.
(see ISO/IEC 11179). This standard specifies a schema for recording both the meaning and technical structure of the data for unambiguous usage by humans and computers. ISO/IEC 11179 standard refers to metadata as information objects about data, or "data about data". In ISO/IEC 11179 Part-3, the information objects are data about Data Elements, Value Domains, and other reusable semantic and representational information objects that describe the meaning and technical details of a data item. This standard also prescribes the details for a metadata registry, and for registering and administering the information objects within a Metadata Registry. ISO/IEC 11179 Part 3 also has provisions for describing compound structures that are derivations of other data elements, for example through calculations, collections of one or more data elements, or other forms of derived data. While this standard describes itself originally as a "data element" registry, its purpose is to support describing and registering metadata content independently of any particular application, lending the descriptions to being discovered and reused by humans or computers in developing new applications, databases, or for analysis of data collected in accordance with the registered metadata content. This standard has become the general basis for other kinds of metadata registries, reusing and extending the registration and administration portion of the standard.

The Geospatial community has a tradition of specialized [[Geospatial metadata|geospatial metadata]] standards, particularly building on traditions of map- and image-libraries and catalogs. Formal metadata is usually essential for geospatial data, as common text-processing approaches are not applicable.

The [[Dublin Core]] metadata terms are a set of vocabulary terms that can be used to describe resources for the purposes of discovery. The original set of 15 classic<ref>{{cite web |url=http://dublincore.org/specifications/ |title=DCMI Specifications |publisher=Dublincore.org |date=14 December 2009 |access-date=17 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20130817110452/http://dublincore.org/specifications/ |archive-date=17 August 2013}}</ref> metadata terms, known as the Dublin Core Metadata Element Set<ref>{{cite web |url=http://dublincore.org/documents/dces/ |title=Dublin Core Metadata Element Set, Version 1.1 |publisher=Dublincore.org |access-date=17 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20130816091758/http://dublincore.org/documents/dces/ |archive-date=16 August 2013}}</ref> are endorsed in the following standards documents:
* IETF RFC 5013<ref>{{cite web |url=http://www.ietf.org/rfc/rfc5013.txt |title=The Dublin Core Metadata Element Set |author=J. Kunze, T. Baker |work=ietf.org |year=2007 |access-date=17 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20130804180251/http://www.ietf.org/rfc/rfc5013.txt |archive-date=4 August 2013}}</ref>
* ISO Standard 15836-2009<ref>{{cite web |url=http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=52142 |title=ISO 15836:2009 – Information and documentation – The Dublin Core metadata element set |publisher=Iso.org |date=18 February 2009 |access-date=17 August 2013 |url-status=live |archive-url=https://web.archive.org/web/20140327062250/http://www.iso.org/iso/iso_catalogue/catalogue_ics/catalogue_detail_ics.htm?csnumber=52142 |archive-date=27 March 2014}}</ref>
* NISO Standard Z39.85.<ref>{{cite web |url=http://www.niso.org/kst/reports/standards?step=2&gid=None&project_key=9b7bffcd2daeca6198b4ee5a848f9beec2f600e5 |title=NISO Standards – National Information Standards Organization |publisher=Niso.org |date=22 May 2007 |access-date=17 August 2013 |url-status=dead |archive-url=https://web.archive.org/web/20111116005843/http://www.niso.org/kst/reports/standards?step=2&gid=None&project_key=9b7bffcd2daeca6198b4ee5a848f9beec2f600e5 |archive-date=16 November 2011}}</ref>

The W3C Data Catalog Vocabulary (DCAT)<ref>{{cite web |url=https://www.w3.org/TR/vocab-dcat/ |title=Data Catalog Vocabulary (DCAT) – Version 2 |publisher=w3.org |date=4 February 2020 |access-date=23 November 2020 |archive-date=8 November 2020 |archive-url=https://web.archive.org/web/20201108112955/http://www.w3.org/TR/vocab-dcat/ |url-status=live}}</ref> is an RDF vocabulary that supplements Dublin Core with classes for Dataset, Data Service, Catalog, and Catalog Record. DCAT also uses elements from FOAF, PROV-O, and OWL-Time. DCAT provides an RDF model to support the typical structure of a catalog that contains records, each describing a dataset or service.

Although not a standard, [[Microformat]] (also mentioned in the section metadata on the internet below) is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata. Microformat follows XHTML and HTML standards but is not a standard in itself. One advocate of microformats, Tantek Çelik, characterized a problem with alternative approaches: {{cquote|Here's a new language we want you to learn, and now you need to output these additional files on your server. It's a hassle. (Microformats) lower the barrier to entry.<ref name="Wharton000">{{cite web |title=What's the Next Big Thing on the Web? It May Be a Small, Simple Thing – Microformats |work=Knowledge@Wharton |publisher=Wharton School of the University of Pennsylvania | date=2005-07-27 |url=http://knowledge.wharton.upenn.edu/index.cfm?fa=printArticle&ID=1247 |access-date=19 August 2012 |archive-date=6 August 2013 |archive-url=https://web.archive.org/web/20130806143629/http://knowledge.wharton.upenn.edu/article.cfm?articleid=1247 |url-status=live}}</ref>}}

== Use ==

=== Photographs ===
Metadata may be written into a digital photo file that will identify who owns it, copyright and contact information, what brand or model of camera created the file, along with exposure information (shutter speed, f-stop, etc.) and descriptive information, such as keywords about the photo, making the file or image searchable on a computer and/or the Internet. Some metadata is created by the camera such as, color space, color channels, exposure time, and aperture (EXIF), while some is input by the photographer and/or software after downloading to a computer.<ref>{{Cite web |title=What is metadata? |url=https://www.ionos.com/digitalguide/websites/web-development/what-is-metadata/ |access-date=17 May 2022 |website=IONOS Digitalguide |language=en |archive-date=17 May 2022 |archive-url=https://web.archive.org/web/20220517135258/https://www.ionos.com/digitalguide/websites/web-development/what-is-metadata/ |url-status=live}}</ref> Most digital cameras write metadata about the model number, shutter speed, etc., and some enable you to edit it;<ref>{{cite web |publisher=gurucamera.com |title=How To Copyright Your Photos With Metadata |url=https://gurucamera.com/copyright-photos-metadata/ |work=Guru Camera |url-status=live |archive-url=https://web.archive.org/web/20160630023616/https://gurucamera.com/copyright-photos-metadata/ |archive-date=30 June 2016 |date=21 May 2016}}</ref> this functionality has been available on most Nikon DSLRs since the [[Engineering:Nikon D3|Nikon D3]], on most new Canon cameras since the [[Engineering:Canon EOS 7D|Canon EOS 7D]], and on most Pentax DSLRs since the Pentax K-3. Metadata can be used to make organizing in post-production easier with the use of key-wording. Filters can be used to analyze a specific set of photographs and create selections on criteria like rating or capture time. On devices with geolocation capabilities like [[Engineering:Global Positioning System|GPS]] (smartphones in particular), the location the photo was taken from may also be included.

Photographic Metadata Standards are governed by organizations that develop the following standards. They include, but are not limited to:
* [[IPTC Information Interchange Model]] IIM (International Press Telecommunications Council)
* [[Organization:International Press Telecommunications Council|IPTC]] Core Schema for XMP
* [[Extensible Metadata Platform|XMP]] – Extensible Metadata Platform (an ISO standard)
* Exif – Exchangeable image file format, Maintained by CIPA (Camera & Imaging Products Association) and published by JEITA (Japan Electronics and Information Technology Industries Association)
* [[Dublin Core]] (Dublin Core Metadata Initiative – DCMI)
* PLUS (Picture Licensing Universal System)
* VRA Core (Visual Resource Association)<ref>{{cite web |title=VRA Core Support Pages |url=http://core.vraweb.org/ |website=Visual Resource Association Foundation |access-date=27 February 2016 |url-status=live |archive-url=https://web.archive.org/web/20160409191705/http://core.vraweb.org/ |archive-date=9 April 2016}}</ref>

=== Telecommunications ===
Information on the times, origins and destinations of phone calls, electronic messages, instant messages, and other modes of telecommunication, as opposed to message content, is another form of metadata. Bulk collection of this call detail record metadata by intelligence agencies has proven controversial after disclosures by Edward Snowden of the fact that certain Intelligence agencies such as the NSA had been (and perhaps still are) keeping online metadata on millions of internet users for up to a year, regardless of whether or not they [ever] were persons of interest to the agency.

=== Video ===
Metadata is particularly useful in video, where information about its contents (such as transcripts of conversations and text descriptions of its scenes) is not directly understandable by a computer, but where an efficient search of the content is desirable. This is particularly useful in video applications such as [[Automatic number-plate recognition|Automatic Number Plate Recognition]] and Vehicle Recognition Identification software, wherein license plate data is saved and used to create reports and alerts.<ref>{{Cite web |url=https://www.dhs.gov/sites/default/files/publications/LPRStandards-TN_1012-508.pdf |title=System Assessment and Validation for Emergency Responders (SAVER) |last=Homeland Security |date=October 2012 |access-date=30 January 2018 |archive-date=31 January 2018 |archive-url=https://web.archive.org/web/20180131080908/https://www.dhs.gov/sites/default/files/publications/LPRStandards-TN_1012-508.pdf |url-status=live}}</ref> There are 2 sources in which video metadata is derived: (1) operational gathered metadata, that is information about the content produced, such as the type of equipment, software, date, and location; (2) human-authored metadata, to improve search engine visibility, discoverability, audience engagement, and providing advertising opportunities to video publishers.<ref>{{cite web |last=Webcase |first=Weblog |title=Examining video file metadata |year=2011 |url=http://veresoftware.com/blog/?p=364 |access-date=25 November 2015 |url-status=live |archive-url=https://web.archive.org/web/20151126114622/http://veresoftware.com/blog/?p=364 |archive-date=26 November 2015}}</ref> Avid's MetaSync and Adobe's Bridge are examples of professional video editing software with access to metadata.<ref>{{cite web |last=Oak Tree Press |title=Metadata for Video |year=2011 |url=http://veresoftware.com/blog/?p=364 |access-date=25 November 2015 |url-status=live |archive-url=https://web.archive.org/web/20151126114622/http://veresoftware.com/blog/?p=364 |archive-date=26 November 2015}}</ref>

=== Geospatial metadata ===
{{Main|Geospatial metadata}}
Geospatial metadata relates to Geographic Information Systems (GIS) files, maps, images, and other data that is location-based. Metadata is used in GIS to document the characteristics and attributes of geographic data, such as database files and data that is developed within a GIS. It includes details like who developed the data, when it was collected, how it was processed, and what formats it's available in, and then delivers the context for the data to be used effectively.<ref>{{Cite web |url=https://www.fgdc.gov/metadata |title=Geospatial Metadata – Federal Geographic Data Committee |website=www.fgdc.gov |access-date=10 October 2019 |archive-date=27 September 2019 |archive-url=https://web.archive.org/web/20190927034722/https://www.fgdc.gov/metadata |url-status=live}}</ref>

== Creation ==
Metadata can be created either by automated information processing or by manual work. Elementary metadata captured by computers can include information about when an object was created, who created it, when it was last updated, file size, and file extension. In this context an ''object'' refers to any of the following:
* A physical item such as a book, CD, DVD, a paper map, chair, table, flower pot, etc.
* An electronic file such as a digital image, digital photo, electronic document, program file, database table, etc.

A [[Metadata engine|metadata engine]] collects, stores and analyzes information about data and metadata in use within a domain.<ref>{{cite web |last1=Kendall |first1=Aaron |title=Metadata-Driven Design: Designing a Flexible Engine for API Data Retrieval |url=https://www.infoq.com/articles/mdd-api-data-retrieval |website=InfoQ |accessdate=25 April 2017 |ref=1 |archive-date=26 April 2017 |archive-url=https://web.archive.org/web/20170426060208/https://www.infoq.com/articles/mdd-api-data-retrieval |url-status=live}}</ref>

=== Data virtualization ===
{{Main|Data virtualization}}
Data virtualization emerged in the 2000s as the new software technology to complete the virtualization "stack" in the enterprise. Metadata is used in data virtualization servers which are enterprise infrastructure components, alongside database and application servers. Metadata in these servers is saved as persistent repository and describe [[Business object|business object]]s in various enterprise systems and applications. Structural metadata commonality is also important to support data virtualization.

=== Statistics and census services ===
Standardization and harmonization work has brought advantages to industry efforts to build metadata systems in the statistical community.<ref name="GløersenImprov11">{{cite web |url=https://www.unece.org/fileadmin/DAM/stats/documents/ece/ces/ge.50/2011/wp.11.e.pdf |title=Improving interoperability in Statistics – The impact of SDMX: Some Considerations |author=Gløersen, R. |publisher=United Nations Economic Commission for Europe |date=30 April 2011 |access-date=17 May 2018 |archive-date=17 May 2018 |archive-url=https://web.archive.org/web/20180517165424/https://www.unece.org/fileadmin/DAM/stats/documents/ece/ces/ge.50/2011/wp.11.e.pdf |url-status=live}}</ref><ref name="LaurilaMetadata12">{{cite web |url=https://ec.europa.eu/eurostat/cros/system/files/NTTS2013fullPaper_182.pdf |title=Metadata system meeting requirements of standardisation, quality and interaction and integrity with other metadata systems: Case Variable Editor Statistics Finland |author=Laurila, S. |publisher=European Commission |date=21 December 2012 |access-date=17 May 2018 |archive-date=2 May 2018 |archive-url=https://web.archive.org/web/20180502014606/https://ec.europa.eu/eurostat/cros/system/files/NTTS2013fullPaper_182.pdf |url-status=live}}</ref> Several metadata guidelines and standards such as the European Statistics Code of Practice<ref name="ECEuropeanStat">{{cite web |url=http://ec.europa.eu/eurostat/web/quality/european-statistics-code-of-practice |title=European Statistics Code of Practice |publisher=European Commission |access-date=17 May 2018 |archive-date=19 May 2018 |archive-url=https://web.archive.org/web/20180519035130/http://ec.europa.eu/eurostat/web/quality/european-statistics-code-of-practice |url-status=live}}</ref> and ISO 17369:2013 ([[SDMX|Statistical Data and Metadata Exchange]] or SDMX)<ref name="GløersenImprov11" /> provide key principles for how businesses, government bodies, and other entities should manage statistical data and metadata. Entities such as Eurostat,<ref name="UNReportOn15">{{cite web |url=https://unstats.un.org/unsd/statcom/doc15/2015-33-SDMX-E.pdf |title=Report on the Statistical Data and Metadata Exchange sponsors |author=Economic and Social Council, Statistical Commission |publisher=United Nations |date=3 March 2015 |access-date=18 May 2018 |archive-date=21 June 2019 |archive-url=https://web.archive.org/web/20190621214021/https://unstats.un.org/unsd/statcom/doc15/2015-33-SDMX-E.pdf |url-status=live}}</ref> European System of Central Banks,<ref name="UNReportOn15" /> and the U.S. Environmental Protection Agency<ref name="EPAMetadata17">{{cite web |url=https://www.epa.gov/geospatial/epa-metadata-technical-specification |title=EPA Metadata Technical Specification |publisher=U.S. Environmental Protection Agency |date=15 August 2017 |access-date=18 May 2018 |archive-date=19 May 2018 |archive-url=https://web.archive.org/web/20180519120704/https://www.epa.gov/geospatial/epa-metadata-technical-specification |url-status=live}}</ref> have implemented these and other such standards and guidelines with the goal of improving "efficiency when managing statistical business processes".<ref name="UNReportOn15" />

=== Library and information science ===
Metadata has been used in various ways as a means of cataloging items in libraries in both digital and analog formats. Such data helps classify, aggregate, identify, and locate a particular book, DVD, magazine, or any object a library might hold in its collection.<ref>{{Cite journal |last1=Zavalina |first1=Oksana L. |last2=Zavalin |first2=Vyacheslav |last3=Shakeri |first3=Shadi |last4=Kizhakkethil |first4=Priya |date=2016 |title=Developing an Empirically-based Framework of Metadata Change and Exploring Relation between Metadata Change and Metadata Quality in MARC Library Metadata |journal=Procedia Computer Science |language=en |volume=99 |pages=50–63 |doi=10.1016/j.procs.2016.09.100 |doi-access=free }}</ref> Until the 1980s, many library catalogs used 3x5 inch cards in file drawers to display a book's title, author, subject matter, and an abbreviated [[Alphanumeric|alpha-numeric]] string (call number) which indicated the physical location of the book within the library's shelves. The [[Dewey Decimal Classification|Dewey Decimal System]] employed by libraries for the classification of library materials by subject is an early example of metadata usage. The early paper catalog had information regarding whichever item was described on said card: title, author, subject, and a number as to where to find said item.<ref>{{cite web |url=https://protekvaults.com/blog/metadata/#:~:text=Over%20the%20last%20135%2Dyears,sundries%2C%20all%20over%20the%20world. |title=What is metadata? |website=Pro-Tek Vaults |date=11 January 2012 |access-date=13 July 2022 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714012002/https://protekvaults.com/blog/metadata/#:~:text=Over%20the%20last%20135%2Dyears,sundries%2C%20all%20over%20the%20world. |url-status=live}}</ref> Beginning in the 1980s and 1990s, many libraries replaced these paper file cards with computer databases. These computer databases make it much easier and faster for users to do keyword searches. Another form of older metadata collection is the use by the US Census Bureau of what is known as the "Long Form". The Long Form asks questions that are used to create demographic data to find patterns of distribution.<ref>{{cite web |title=AGLS Metadata Element Set – Part 2: Usage Guide – A non-technical guide to using AGLS metadata for describing resources |author=National Archives of Australia |year=2002 |url=http://www.naa.gov.au/records-management/publications/agls-element.aspx |access-date=17 March 2010 |url-status=live |archive-url=https://web.archive.org/web/20100330095200/http://www.naa.gov.au/records-management/publications/agls-element.aspx |archive-date=30 March 2010}}</ref> Libraries employ metadata in [[Library catalog|library catalog]]ues, most commonly as part of an Integrated Library Management System. Metadata is obtained by cataloging resources such as books, periodicals, DVDs, web pages or digital images. This data is stored in the integrated library management system, ILMS, using the [[MARC standards|MARC]] metadata standard. The purpose is to direct patrons to the physical or electronic location of items or areas they seek as well as to provide a description of the item/s in question.

More recent and specialized instances of library metadata include the establishment of [[Digital library|digital libraries]] including [[Eprint|e-print]] repositories and digital image libraries. While often based on library principles, the focus on non-librarian use, especially in providing metadata, means they do not follow traditional or common cataloging approaches. Given the custom nature of included materials, metadata fields are often specially created e.g. taxonomic classification fields, location fields, keywords, or copyright statement. Standard file information such as file size and format are usually automatically included.<ref name="solodovnik">{{cite journal |last1=Solodovnik |first1=Iryna |year=2011 |title=Metadata issues in Digital Libraries: key concepts and perspectives |journal=JLIS.it | volume=2 |issue=2 |publisher=University of Florence |doi=10.4403/jlis.it-4663 |url=http://leo.cilea.it/index.php/jlis/article/view/4663 |access-date=29 June 2013 |url-status=live |archive-url=https://web.archive.org/web/20130616093855/http://leo.cilea.it/index.php/jlis/article/view/4663 |archive-date=16 June 2013}}</ref> Library operation has for decades been a key topic in efforts toward international standardization. Standards for metadata in digital libraries include [[Dublin Core]], [[Metadata Encoding and Transmission Standard|METS]], [[Metadata Object Description Schema|MODS]], [[Data Documentation Initiative|DDI]], [[Digital object identifier|DOI]], [[Uniform Resource Name|URN]], [[Preservation Metadata: Implementation Strategies|PREMIS]] schema, [[Ecological Metadata Language|EML]], and OAI-PMH. Leading libraries in the world give hints on their metadata standards strategies.<ref>{{cite web |author=Library of Congress Network Development and MARC Standards Office |url=https://www.loc.gov/standards/metadata.html |title=Library of Congress Washington DC on metadata |publisher=Loc.gov |date=8 September 2005 |access-date=23 December 2011 |url-status=live |archive-url=https://web.archive.org/web/20111215031826/http://www.loc.gov/standards/metadata.html |archive-date=15 December 2011}}</ref><ref>{{cite web |url=http://www.dnb.de/DE/Netzpublikationen/Ablieferung/MetadatenKernset/metadatenkernset_node.html |title=Deutsche Nationalbibliothek Frankfurt on metadata |url-status=dead |archive-url=https://web.archive.org/web/20121024122607/http://www.dnb.de/DE/Netzpublikationen/Ablieferung/MetadatenKernset/metadatenkernset_node.html |archive-date=24 October 2012 |access-date=23 October 2012}}</ref> The use and creation of metadata in library and information science also include scientific publications:

=== Science ===
{{Further|Metascience}}
[[File:FREYA-The-power-of-PIDs-V05-1.webm|thumb|thumbtime=0:30|An introduction to [[FAIR data|FAIR data]] and [[Persistent identifier|persistent identifier]]s]]
Metadata for scientific<!--, e.g. biomedical--> publications is often created by journal publishers and citation databases such as [[Biology:PubMed|PubMed]] and Web of Science. The data contained within manuscripts or accompanying them as supplementary material is less often subject to metadata creation,<ref>{{Cite journal |last1=Evangelou |first1=Evangelos |last2=Trikalinos |first2=Thomas A. |last3=Ioannidis |first3=John P.A. |date=2005 |title=Unavailability of online supplementary scientific information from articles published in major journals |journal=The FASEB Journal |language=en |volume=19 |issue=14 |pages=1943–1944 |doi=10.1096/fj.05-4784lsf |doi-access=free |pmid=16319137 |s2cid=24245004 |issn=0892-6638 }}</ref><ref>{{Cite journal |last1=AlQuraishi |first1=Mohammed |last2=Sorger |first2=Peter K. |date=18 May 2016 |title=Reproducibility will only come with data liberation |journal=Science Translational Medicine |language=en |volume=8 |issue=339 |pages=339ed7 |doi=10.1126/scitranslmed.aaf0968 |issn=1946-6234 |pmc=5084089 |pmid=27194726}}</ref> though they may be submitted to e.g. biomedical databases after publication. The original authors and database curators then become responsible for metadata creation, with the assistance of automated processes. Comprehensive metadata for all experimental data is the foundation of the [[FAIR data|FAIR Guiding Principles]], or the standards for ensuring research data are [[Findability|findable]], [[Engineering:Accessibility|accessible]], [[Engineering:Interoperability|interoperable]], and [[Reusability|reusable]].<ref>{{Cite journal |last1=Wilkinson |first1=Mark D. |last2=Dumontier |first2=Michel |last3=Aalbersberg |first3=IJsbrand Jan |last4=Appleton |first4=Gabrielle |last5=Axton |first5=Myles |last6=Baak |first6=Arie |last7=Blomberg |first7=Niklas |last8=Boiten |first8=Jan-Willem |last9=da Silva Santos |first9=Luiz Bonino |date=15 March 2016 |title=The FAIR Guiding Principles for scientific data management and stewardship |journal=Scientific Data |language=En |volume=3 |pages=160018 |doi=10.1038/sdata.2016.18 |issn=2052-4463 |pmc=4792175 |pmid=26978244 |bibcode=2016NatSD...360018W}}</ref>

Such metadata can then be utilized, complemented, and made accessible in useful ways. [[Our Research#OpenAlex|OpenAlex]] is a free online index of over 200 million scientific documents that integrates and provides metadata such as sources, [[Scientific citation|citations]], [[Academic authorship|author information]], scientific fields, and research topics. Its [[API]] and open source website can be used for metascience, [[Scientometrics|scientometrics]], and novel tools that query this [[Semantic Web|semantic]] web of papers.<ref>{{cite news |last1=Singh Chawla |first1=Dalmeet |title=Massive open index of scholarly papers launches |url=https://www.nature.com/articles/d41586-022-00138-y |access-date=14 February 2022 |journal=Nature |date=24 January 2022 |language=en |doi=10.1038/d41586-022-00138-y |archive-date=7 February 2022 |archive-url=https://web.archive.org/web/20220207140943/https://www.nature.com/articles/d41586-022-00138-y |url-status=live}}</ref><ref>{{cite news |title=OpenAlex: The Promising Alternative to Microsoft Academic Graph |url=https://library.smu.edu.sg/topics-insights/openalex-promising-alternative-microsoft-academic-graph |access-date=14 February 2022 |work=Singapore Management University (SMU) |language=en |archive-date=14 February 2022 |archive-url=https://web.archive.org/web/20220214174827/https://library.smu.edu.sg/topics-insights/openalex-promising-alternative-microsoft-academic-graph |url-status=live}}</ref><ref>{{cite web |title=OpenAlex Documentation |url=https://docs.openalex.org/ |access-date=18 February 2022 |archive-date=2 February 2022 |archive-url=https://web.archive.org/web/20220202002019/https://docs.openalex.org/ |url-status=live}}</ref> Another project under development, Scholia, uses the metadata of scientific publications for various visualizations and aggregation features such as providing a simple user interface summarizing literature about a specific feature of the SARS-CoV-2 virus using [[Wikidata]]'s "main subject" property.<ref name="10.1186/s12915-020-00940-y">{{cite journal |last1=Waagmeester |first1=Andra |last2=Willighagen |first2=Egon L. |last3=Su |first3=Andrew I. |last4=Kutmon |first4=Martina |last5=Gayo |first5=Jose Emilio Labra |last6=Fernández-Álvarez |first6=Daniel |last7=Groom |first7=Quentin |last8=Schaap |first8=Peter J. |last9=Verhagen |first9=Lisa M. |last10=Koehorst |first10=Jasper J. |title=A protocol for adding knowledge to Wikidata: aligning resources on human coronaviruses |journal=BMC Biology |date=22 January 2021 |volume=19 |issue=1 |pages=12 |doi=10.1186/s12915-020-00940-y |pmid=33482803 |pmc=7820539 |issn=1741-7007 |doi-access=free }}</ref>

In research labor, transparent metadata about authors' contributions to works have been proposed – e.g. the role played in the production of the paper, the level of contribution and the responsibilities.<ref>{{cite journal |last1=McNutt |first1=Marcia K. |last2=Bradford |first2=Monica |last3=Drazen |first3=Jeffrey M. |last4=Hanson |first4=Brooks |last5=Howard |first5=Bob |last6=Jamieson |first6=Kathleen Hall |last7=Kiermer |first7=Véronique |last8=Marcus |first8=Emilie |last9=Pope |first9=Barbara Kline |last10=Schekman |first10=Randy |last11=Swaminathan |first11=Sowmya |last12=Stang |first12=Peter J. |last13=Verma |first13=Inder M. |title=Transparency in authors' contributions and responsibilities to promote integrity in scientific publication |journal=Proceedings of the National Academy of Sciences |date=13 March 2018 |volume=115 |issue=11 |pages=2557–2560 |doi=10.1073/pnas.1715374115 |pmid=29487213 |pmc=5856527 |bibcode=2018PNAS..115.2557M |language=en |issn=0027-8424 |doi-access=free}}</ref><ref>{{cite journal |last1=Brand |first1=Amy |last2=Allen |first2=Liz |last3=Altman |first3=Micah |last4=Hlava |first4=Marjorie |last5=Scott |first5=Jo |title=Beyond authorship: attribution, contribution, collaboration, and credit |journal=Learned Publishing |date=1 April 2015 |volume=28 |issue=2 |pages=151–155 |doi=10.1087/20150211 |s2cid=45167271 |url=https://www.researchgate.net/publication/274098676|doi-access=free }}</ref>

Moreover, various metadata about scientific outputs can be created or complemented – for instance, scite.ai attempts to track and link citations of papers as 'Supporting', 'Mentioning' or 'Contrasting' the study.<ref>{{cite news |last1=Khamsi |first1=Roxanne |title=Coronavirus in context: Scite.ai tracks positive and negative citations for COVID-19 literature |url=https://www.nature.com/articles/d41586-020-01324-6 |access-date=19 February 2022 |journal=Nature |date=1 May 2020 |language=en |doi=10.1038/d41586-020-01324-6 |archive-date=19 February 2022 |archive-url=https://web.archive.org/web/20220219212737/https://www.nature.com/articles/d41586-020-01324-6 |url-status=live}}</ref> Other examples include developments of [[Altmetrics|alternative metrics]]<ref name="10.1126/science.aao0185">{{cite journal |last1=Fortunato |first1=Santo |last2=Bergstrom |first2=Carl T. |last3=Börner |first3=Katy |last4=Evans |first4=James A. |last5=Helbing |first5=Dirk |last6=Milojević |first6=Staša |last7=Petersen |first7=Alexander M. |last8=Radicchi |first8=Filippo |last9=Sinatra |first9=Roberta |last10=Uzzi |first10=Brian |last11=Vespignani |first11=Alessandro |last12=Waltman |first12=Ludo |last13=Wang |first13=Dashun |last14=Barabási |first14=Albert-László |title=Science of science |journal=Science |date=2 March 2018 |volume=359 |issue=6379 |pages=eaao0185 |doi=10.1126/science.aao0185 |pmid=29496846 |pmc=5949209 |url=https://www.researchgate.net/publication/323502497 |access-date=22 November 2021}}</ref> – which, beyond providing help for assessment and findability, also aggregate many of the public discussions about a scientific paper on social media such as [[Company:Reddit|Reddit]], citations on Wikipedia, and [[Science communication|reports about the study]] in the news media<ref>{{cite journal |last1=Baykoucheva |first1=Svetla |title=Measuring attention |journal=Managing Scientific Information and Research Data |date=2015 |pages=127–136 |doi=10.1016/B978-0-08-100195-0.00014-7 |isbn=978-0-08-100195-0 |url=https://www.researchgate.net/publication/280568406}}</ref> – and a call for showing [[Reproducibility|whether or not the original findings are confirmed or could get reproduced]].<ref>{{cite news |title=A new replication crisis: Research that is less likely to be true is cited more |url=https://phys.org/news/2021-05-replication-crisis-true-cited.html |access-date=14 June 2021 |work=phys.org |language=en |archive-date=13 June 2021 |archive-url=https://web.archive.org/web/20210613043457/https://phys.org/news/2021-05-replication-crisis-true-cited.html |url-status=live}}</ref><ref>{{cite journal |last1=Serra-Garcia |first1=Marta |last2=Gneezy |first2=Uri |title=Nonreplicable publications are cited more than replicable ones |journal=Science Advances |date=1 May 2021 |volume=7 |issue=21 |pages=eabd1705 |doi=10.1126/sciadv.abd1705 |pmid=34020944 |pmc=8139580 |bibcode=2021SciA....7.1705S |language=en |issn=2375-2548}}</ref>

=== Museums ===
Metadata in a museum context is the information that trained cultural documentation specialists, such as [[Social:Archivist|archivist]]s, librarians, museum registrars and [[Social:Curator|curator]]s, create to index, structure, describe, identify, or otherwise specify works of art, architecture, cultural objects and their images.<ref name=":0">{{Cite web |last=Zange |first=Charles S. |date=31 January 2015 |title=Community makers, major museums, and the Keet S'aaxw: Learning about the role of museums in interpreting cultural objects |url=http://mw2015.museumsandtheweb.com/paper/community-makers-major-museums-and-the-keet-saaxw-learning-about-the-role-of-museums-in-interpreting-cultural-objects/ |publisher=Museums and the Web |url-status=live |archive-url=https://web.archive.org/web/20161104005603/http://mw2015.museumsandtheweb.com/paper/community-makers-major-museums-and-the-keet-saaxw-learning-about-the-role-of-museums-in-interpreting-cultural-objects/ |archive-date=4 November 2016}}</ref><ref name=":1">{{Cite book |title=Cataloging cultural objects: a guide to describing cultural works and their images. Visual Resources Association |last=Baca |first=Murtha |publisher=Visual Resources Association |year=2006 |page=4}}</ref><ref name=":2">{{Cite book |title=Introduction to Metadata: Second Edition. Los Angeles: Getty Information Institute |last=Baca |first=Murtha |publisher=Getty Information Institute |year=2008 |location=Los Angeles |page=11}}</ref> Descriptive metadata is most commonly used in museum contexts for object identification and resource recovery purposes.<ref name=":1" />

==== Usage ====
Metadata is developed and applied within collecting institutions and museums in order to:
* Facilitate resource discovery and execute search queries.<ref name=":2" />
* Create digital archives that store information relating to various aspects of museum collections and cultural objects, and serve archival and managerial purposes.<ref name=":2" />
* Provide public audiences access to cultural objects through publishing digital content online.<ref name=":1" /><ref name=":2" />

==== Standards ====
Many museums and cultural heritage centers recognize that given the diversity of artworks and cultural objects, no single model or standard suffices to describe and catalog cultural works.<ref name=":0" /><ref name=":1" /><ref name=":2" /> For example, a sculpted Indigenous artifact could be classified as an artwork, an archaeological artifact, or an Indigenous heritage item. The early stages of standardization in archiving, description and cataloging within the museum community began in the late 1990s with the development of standards such as Categories for the Description of Works of Art (CDWA), Spectrum, [[CIDOC Conceptual Reference Model]] (CRM), Cataloging Cultural Objects (CCO) and the CDWA Lite XML schema.<ref name=":1" /> These standards use [[HTML]] and [[XML]] markup languages for machine processing, publication and implementation.<ref name=":1" /> The [[Anglo-American Cataloguing Rules]] (AACR), originally developed for characterizing books, have also been applied to cultural objects, works of art and architecture.<ref name=":2" /> Standards, such as the CCO, are integrated within a Museum's Collections Management System (CMS), a database through which museums are able to manage their collections, acquisitions, loans and conservation.<ref name=":2" /> Scholars and professionals in the field note that the "quickly evolving landscape of standards and technologies" creates challenges for cultural documentarians, specifically non-technically trained professionals.<ref name=":3">{{Cite book |title=Linked Data for Libraries, Archives and Museums: How to Clean, Link and Publish Your Metadata |last1=Hooland |first1=Seth Van |last2=Verborgh |first2=Ruben |publisher=Facet |year=2014 |location=London}}</ref>{{page needed|date=November 2016}} Most collecting institutions and museums use a [[Relational database|relational database]] to categorize cultural works and their images.<ref name=":2" /> Relational databases and metadata work to document and describe the complex relationships amongst cultural objects and multi-faceted works of art, as well as between objects and places, people, and artistic movements.<ref name=":1" /><ref name=":2" /> Relational database structures are also beneficial within collecting institutions and museums because they allow for archivists to make a clear distinction between cultural objects and their images; an unclear distinction could lead to confusing and inaccurate searches.<ref name=":2" />

==== Cultural objects ====
An object's materiality, function, and purpose, as well as the size (e.g., measurements, such as height, width, weight), storage requirements (e.g., climate-controlled environment), and focus of the museum and collection, influence the descriptive depth of the data attributed to the object by cultural documentarians.<ref name=":2" /> The established institutional cataloging practices, goals, and expertise of cultural documentarians and database structure also influence the information ascribed to cultural objects and the ways in which cultural objects are categorized.<ref name=":0" /><ref name=":2" /> Additionally, museums often employ standardized commercial collection management software that prescribes and limits the ways in which archivists can describe artworks and cultural objects.<ref name=":3" /> As well, collecting institutions and museums use [[Controlled vocabulary|Controlled Vocabularies]] to describe cultural objects and artworks in their collections.<ref name=":1" /><ref name=":2" /> Getty Vocabularies and the Library of Congress Controlled Vocabularies are reputable within the museum community and are recommended by CCO standards.<ref name=":2" /> Museums are encouraged to use controlled vocabularies that are contextual and relevant to their collections and enhance the functionality of their digital information systems.<ref name=":1" /><ref name=":2" /> Controlled Vocabularies are beneficial within databases because they provide a high level of consistency, improving resource retrieval.<ref name=":1" /><ref name=":2" /> Metadata structures, including controlled vocabularies, reflect the [[Ontology (information science)|ontologies]] of the systems from which they were created. Often the processes through which cultural objects are described and categorized through metadata in museums do not reflect the perspectives of the maker communities.<ref name=":0" /><ref>{{Cite journal |last=Srinivasan |first=Ramesh |date=December 2006 |title=Indigenous, ethnic and cultural articulations of new media |journal=International Journal of Cultural Studies |volume=9 |issue=4 |pages=497–518 |doi=10.1177/1367877906069899 |s2cid=145278668 |url=http://www.escholarship.org/uc/item/40p4k54t |access-date=9 December 2019 |archive-date=9 November 2020 |archive-url=https://web.archive.org/web/20201109215925/https://escholarship.org/uc/item/40p4k54t |url-status=live}}</ref>

==== Online content ====
Metadata has been instrumental in the creation of digital information systems and archives within museums and has made it easier for museums to publish digital content online. This has enabled audiences who might not have had access to cultural objects due to geographic or economic barriers to have access to them.<ref name=":1" /> In the 2000s, as more museums have adopted archival standards and created intricate databases, discussions about [[Linked data|Linked Data]] between museum databases have come up in the museum, archival, and library science communities.<ref name=":3" /> Collection Management Systems (CMS) and [[Digital asset management|Digital Asset Management]] tools can be local or shared systems.<ref name=":2" /> [[Digital humanities|Digital Humanities]] scholars note many benefits of interoperability between museum databases and collections, while also acknowledging the difficulties of achieving such interoperability.<ref name=":3" />

=== Law ===
{{Globalize
| date=March 2015
}}

==== United States ====
Problems involving metadata in litigation in the {{wipe|United States}} are becoming widespread.{{when|date=February 2011}} Courts have looked at various questions involving metadata, including the [[Discovery (law)|discoverability]] of metadata by parties. The Federal Rules of Civil Procedure have specific rules for discovery of electronically stored information, and subsequent case law applying those rules has elucidated on the litigant's duty to produce metadata when litigating in federal court.<ref>{{Cite journal |last=Gelzer |first=Reed D. |title=Metadata, Law, and the Real World: Slowly, the Three Are Merging |journal=Journal of AHIMA |volume=79 |issue=2 |pages=56–57, 64 |publisher=American Health Information Management Association |date=February 2008 |url=http://library.ahima.org/xpedio/groups/public/documents/ahima/bok1_036537.hcsp?dDocName=bok1_036537 |access-date=8 January 2010 |url-status=live |archive-url=https://web.archive.org/web/20100913081849/http://library.ahima.org/xpedio/groups/public/documents/ahima/bok1_036537.hcsp?dDocName=bok1_036537 |archive-date=13 September 2010}}</ref> In October 2009, the Arizona Supreme Court has ruled that metadata records are public record.<ref>{{Cite news |last=Walsh |first=Jim |title=Ariz. Supreme Court rules electronic data is public record |newspaper=The Arizona Republic |location=Phoenix, Arizona |date=30 October 2009 |url=http://www.azcentral.com/arizonarepublic/local/articles/2009/10/30/20091030metadata1030.html |access-date=8 January 2010}}</ref> Document metadata have proven particularly important in legal environments in which litigation has requested metadata, that can include sensitive information detrimental to a certain party in court. Using [[Metadata removal tool|metadata removal tool]]s to "clean" or redact documents can mitigate the risks of unwittingly sending sensitive data. This process partially (see [[Data remanence|data remanence]]) protects law firms from potentially damaging leaking of sensitive data through [[Electronic discovery|electronic discovery]].

Opinion polls have shown that 45% of Americans are "not at all confident" in the ability of social media sites to ensure their personal data is secure and 40% say that social media sites should not be able to store any information on individuals. 76% of Americans say that they are not confident that the information advertising agencies collect on them is secure and 50% say that online advertising agencies should not be allowed to record any of their information at all.<ref>{{Cite news |url=http://www.pewinternet.org/2015/05/20/americans-attitudes-about-privacy-security-and-surveillance/ |title=Americans' Attitudes About Privacy, Security and Surveillance {{!}} Pew Research Center|date=20 May 2015|work=Pew Research Center: Internet, Science & Tech|access-date=24 October 2018|language=en-US|archive-date=25 October 2018|archive-url=https://web.archive.org/web/20181025071051/http://www.pewinternet.org/2015/05/20/americans-attitudes-about-privacy-security-and-surveillance/|url-status=live}}</ref>

==== Australia ====
In Australia, the need to strengthen national security has resulted in the introduction of a new metadata storage law.<ref>Senate passes controversial metadata laws</ref> This new law means that both security and policing agencies will be allowed to access up to 2 years of an individual's metadata, with the aim of making it easier to stop any terrorist attacks and serious crimes from happening.

=== Legislation ===
Legislative metadata has been the subject of some discussion in [https://public.resource.org/law.gov/ law.gov] forums such as workshops held by the Legal Information Institute at the Cornell Law School on 22 and 23 March 2010. The documentation for these forums is titled, "Suggested metadata practices for legislation and regulations".<ref>{{Cite web |url=https://www.law.cornell.edu/wiki/lexcraft/suggested_metadata_practices_for_legislation_and_regulations |title=Suggested metadata practices for legislation and regulations |website=Legal Information Institute |date=27 March 2010 |access-date=17 April 2018 |archive-date=9 October 2016 |archive-url=https://web.archive.org/web/20161009080703/https://www.law.cornell.edu/wiki/lexcraft/suggested_metadata_practices_for_legislation_and_regulations |url-status=live}}</ref>

A handful of key points have been outlined by these discussions, section headings of which are listed as follows:
* General Considerations
* Document Structure
* Document Contents
* Metadata (elements of)
* Layering
* Point-in-time versus post-hoc

=== Healthcare ===
Australian medical research pioneered the definition of metadata for applications in health care. That approach offers the first recognized attempt to adhere to international standards in medical sciences instead of defining a proprietary standard under the [[Organization:World Health Organization|World Health Organization]] (WHO) umbrella. The medical community yet did not approve of the need to follow metadata standards despite research that supported these standards.<ref>M. Löbe, M. Knuth, R. Mücke [http://ceur-ws.org/Vol-559/Paper1.pdf TIM: A Semantic Web Application for the Specification of Metadata Items in Clinical Research] {{webarchive|url=https://web.archive.org/web/20120511114907/http://ceur-ws.org/Vol-559/Paper1.pdf |date=11 May 2012 }}, CEUR-WS.org, urn:nbn:de:0074-559-9</ref>

=== Biomedical researches ===
Research studies in the fields of [[Medicine:Biomedicine|biomedicine]] and [[Biology:Molecular biology|molecular biology]] frequently yield large quantities of data, including results of [[Biology:Genome|genome]] or [[Biology:Metagenomics|meta-genome]] [[Biology:Sequencing|sequencing]], [[Biology:Proteomics|proteomics]] data, and even notes or plans created during the course of research itself.<ref>{{Cite journal |last1=Myneni |first1=Sahiti |last2=Patel |first2=Vimla L. |date=1 June 2010 |title=Organization of Biomedical Data for Collaborative Scientific Research: A Research Information Management System |journal=International Journal of Information Management |volume=30 |issue=3 |pages=256–264 |doi=10.1016/j.ijinfomgt.2009.09.005 |issn=0268-4012 |pmc=2882303 |pmid=20543892}}</ref> Each data type involves its own variety of metadata and the processes necessary to produce these metadata. General metadata standards, such as ISA-Tab,<ref>{{Cite journal |last1=Sansone |first1=Susanna-Assunta |last2=Rocca-Serra |first2=Philippe |last3=Field |first3=Dawn |last4=Maguire |first4=Eamonn |last5=Taylor |first5=Chris |last6=Hofmann |first6=Oliver |last7=Fang |first7=Hong |last8=Neumann |first8=Steffen |last9=Tong |first9=Weida |date=2012 |title=Toward interoperable bioscience data |journal=Nature Genetics |language=En |volume=44 |issue=2 |pages=121–126 |doi=10.1038/ng.1054 |issn=1061-4036 |pmc=3428019 |pmid=22281772}}</ref> allow researchers to create and exchange experimental metadata in consistent formats. Specific experimental approaches frequently have their own metadata standards and systems: metadata standards for [[Physics:Mass spectrometry|mass spectrometry]] include [[MzML|mzML]]<ref>{{Cite journal |last1=Martens |first1=Lennart |last2=Chambers |first2=Matthew |last3=Sturm |first3=Marc |last4=Kessner |first4=Darren |last5=Levander |first5=Fredrik |last6=Shofstahl |first6=Jim |last7=Tang |first7=Wilfred H. |last8=Römpp |first8=Andreas |last9=Neumann |first9=Steffen |date=1 January 2011 |title=mzML&nbsp;– a Community Standard for Mass Spectrometry Data |journal=Molecular & Cellular Proteomics |language=en |volume=10 |issue=1 |pages=R110.000133 |doi=10.1074/mcp.R110.000133  |doi-access=free |issn=1535-9476 |pmc=3013463 |pmid=20716697}}</ref> and SPLASH,<ref>{{Cite journal |last1=Wohlgemuth |first1=Gert |last2=Mehta |first2=Sajjan S |last3=Mejia |first3=Ramon F |last4=Neumann |first4=Steffen |last5=Pedrosa |first5=Diego |last6=Pluskal |first6=Tomáš |last7=Schymanski |first7=Emma L |last8=Willighagen |first8=Egon L |last9=Wilson |first9=Michael |date=2016 |title=SPLASH, a hashed identifier for mass spectra |journal=Nature Biotechnology |language=En |volume=34 |issue=11 |pages=1099–1101 |doi=10.1038/nbt.3689 |issn=1087-0156 |pmc=5515539 |pmid=27824832}}</ref> while [[XML]]-based standards such as [[Biology:Protein Data Bank|PDBML]]<ref>{{Cite journal |last1=Westbrook |first1=J. |last2=Ito |first2=N. |last3=Nakamura |first3=H. |last4=Henrick |first4=K. |last5=Berman |first5=H. M. |date=27 October 2004 |title=PDBML: the representation of archival macromolecular structure data in XML |url=https://academic.oup.com/bioinformatics/article/21/7/988/268819 |journal=Bioinformatics |language=en |volume=21 |issue=7 |pages=988–992 |doi=10.1093/bioinformatics/bti082 |pmid=15509603 |issn=1367-4803 |doi-access=free |access-date=2 October 2018 |archive-date=7 August 2018 |archive-url=https://web.archive.org/web/20180807191926/https://academic.oup.com/bioinformatics/article/21/7/988/268819 |url-status=live}}</ref> and SRA XML<ref>{{Cite journal |last1=Leinonen |first1=R. |last2=Sugawara |first2=H. |last3=Shumway |first3=M. |date=9 November 2010 |title=The Sequence Read Archive |url= |journal=Nucleic Acids Research |language=en |volume=39 |issue=Database |pages=D19–D21 |doi=10.1093/nar/gkq1019 |issn=0305-1048 |pmc=3013647 |pmid=21062823}}</ref> serve as standards for macromolecular structure and sequencing data, respectively.

The products of biomedical research are generally realized as peer-reviewed manuscripts and these publications are yet another source of data {{See above|#Science}}.

=== Data warehousing ===
A [[Data warehouse|data warehouse]] (DW) is a repository of an organization's electronically stored data. Data warehouses are designed to manage and store the data. Data warehouses differ from [[Business intelligence|business intelligence]] (BI) systems because BI systems are designed to use data to create reports and analyze the information, to provide strategic guidance to management.<ref>Inmon, W.H. Tech Topic: What is a Data Warehouse? Prism Solutions. Volume 1. 1995.</ref> Metadata is an important tool in how data is stored in data warehouses. The purpose of a data warehouse is to house standardized, structured, consistent, integrated, correct, "cleaned" and timely data, extracted from various operational systems in an organization. The extracted data are integrated in the data warehouse environment to provide an enterprise-wide perspective. Data are structured in a way to serve the reporting and analytic requirements. The design of structural metadata commonality using a [[Data modeling|data modeling]] method such as entity-relationship model diagramming is important in any data warehouse development effort. They detail metadata on each piece of data in the data warehouse. An essential component of a [[Data warehouse|data warehouse]]/[[Business intelligence|business intelligence]] system is the metadata and tools to manage and retrieve the metadata. Ralph Kimball<ref>{{Cite book |last=Kimball |first=Ralph |title=The Data Warehouse Lifecycle Toolkit |edition=Second |location=New York |publisher=Wiley |year=2008 |isbn=978-0-470-14977-5 |pages=10, 115–117, 131–132, 140, 154–155}}</ref> describes metadata as the DNA of the data warehouse as metadata defines the elements of the [[Data warehouse|data warehouse]] and how they work together.

Kimball et al.<ref>{{harvnb|Kimball|2008|pages=116–117}}</ref> refers to 3 main categories of metadata: Technical metadata, business metadata and process metadata. Technical metadata is primarily [[Philosophy:Definition|definition]]al, while business metadata and process metadata is primarily [[Philosophy:Description|descriptive]]. The categories sometimes overlap.
* '''Technical metadata''' defines the objects and processes in a DW/BI system, as seen from a technical point of view. The technical metadata includes the system metadata, which defines the data structures such as tables, fields, data types, indexes, and partitions in the relational engine, as well as databases, dimensions, measures, and data mining models. Technical metadata defines the data model and the way it is displayed for the users, with the reports, schedules, distribution lists, and user security rights.
* '''Business metadata''' is content from the data warehouse described in more user-friendly terms. The business metadata tells you what data you have, where they come from, what they mean and what their relationship is to other data in the data warehouse. Business metadata may also serve as documentation for the DW/BI system. Users who browse the data warehouse are primarily viewing the business metadata.
* '''Process metadata''' is used to describe the results of various operations in the data warehouse. Within the [[Extract, transform, load|ETL]] process, all key data from tasks is logged on execution. This includes start time, end time, CPU seconds used, disk reads, disk writes, and rows processed. When troubleshooting the ETL or [[Information retrieval|query]] process, this sort of data becomes valuable. Process metadata is the fact measurement when building and using a DW/BI system. Some organizations make a living out of collecting and selling this sort of data to companies – in that case, the process metadata becomes the business metadata for the fact and dimension tables. Collecting process metadata is in the interest of business people who can use the data to identify the users of their products, which products they are using, and what level of service they are receiving.

=== Internet ===
The [[HTML]] format used to define web pages allows for the inclusion of a variety of types of metadata, from basic descriptive text, dates and keywords to further advanced metadata schemes such as the [[Dublin Core]], [[E-GMS|e-GMS]], and AGLS<ref>National Archives of Australia, AGLS Metadata Standard, accessed 7 January 2010, {{cite web |url=http://www.naa.gov.au/records-management/create-capture-describe/describe/AGLS/index.aspx |title=AGLS Metadata Standard |access-date=7 January 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100110054051/http://www.naa.gov.au/records-management/create-capture-describe/describe/AGLS/index.aspx |archive-date=10 January 2010}}</ref> standards. Pages and files can also be [[Engineering:Geotagging|geotagged]] with [[Earth:Geographic coordinate system|coordinates]], categorized or tagged, including collaboratively such as with [[Folksonomy|folksonomies]].

When media has [[Identifier|identifier]]s set or when such can be generated, information such as file tags and descriptions can be pulled or scraped from the Internet – for example about movies.<ref>{{Cite web |url=https://www.researchgate.net/publication/342622411 |title=Making Use of Affective Features from Media Content Metadata for Better Movie Recommendation Making}}</ref> Various online databases are aggregated and provide metadata for various data. The collaboratively built [[Wikidata]] has identifiers not just for media but also abstract concepts, various objects, and other entities, that can be looked up by humans and machines to retrieve useful information and to link knowledge in other knowledge bases and databases.<ref name="10.1186/s12915-020-00940-y" />

Metadata may be included in the page's header or in a separate file. [[Microformat]]s allow metadata to be added to on-page data in a way that regular web users do not see, but computers, [[Web crawler|web crawler]]s and [[Search engine|search engine]]s can readily access. Many search engines are cautious about using metadata in their ranking algorithms because of exploitation of metadata and the practice of search engine optimization, [[Search engine optimization|SEO]], to improve rankings. See the [[Meta element]] article for further discussion. This cautious attitude may be justified as people, according to Doctorow,<ref>Metacrap: Putting the torch to 7 straw-men of the meta-utopia {{cite web |url=http://www.well.com/~doctorow/metacrap.htm |title=Metacrap: Putting the torch to 7 straw-men of the meta-utopia |access-date=8 May 2007 |url-status=live |archive-url=https://web.archive.org/web/20070508200721/http://www.well.com/~doctorow/metacrap.htm |archive-date=8 May 2007}}</ref> are not executing care and diligence when creating their own metadata and that metadata is part of a competitive environment where the metadata is used to promote the metadata creators own purposes. Studies show that search engines respond to web pages with metadata implementations,<ref>The impact of webpage content characteristics on webpage visibility in search engine results {{cite web |url=http://web.simmons.edu/~braun/467/part_1.pdf |title=The impact of webpage content characteristics on webpage visibility in search engine results (Part I) |access-date=3 April 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120907012709/http://web.simmons.edu/~braun/467/part_1.pdf |archive-date=7 September 2012}}</ref> and Google has an announcement on its site showing the meta tags that its search engine understands.<ref>{{cite web |url=https://support.google.com/webmasters/answer/79812?hl=en/ |title=Meta tags that Google understands |access-date=22 May 2014 |url-status=live |archive-url=https://web.archive.org/web/20140522161805/https://support.google.com/webmasters/answer/79812?hl=en%2F |archive-date=22 May 2014}}</ref> Enterprise search startup [[Company:Swiftype|Swiftype]] recognizes metadata as a relevance signal that webmasters can implement for their website-specific search engine, even releasing their own extension, known as Meta Tags 2.<ref>{{Cite web |url=https://swiftype.com/documentation/meta_tags2 |title=Swiftype-specific Meta Tags |work=Swiftype Documentation |publisher=Swiftype |date=3 October 2014 |url-status=live |archive-url=https://web.archive.org/web/20141006113157/https://swiftype.com/documentation/meta_tags2 |archive-date=6 October 2014}}</ref>

=== Broadcast industry ===
In the broadcast industry, metadata is linked to audio and video broadcast media to:
* ''identify'' the media: [[Social:Media clip|clip]] or [[Playlist|playlist]] names, duration, [[Timecode|timecode]], etc.
* ''describe'' the content: notes regarding the quality of video content, rating, description (for example, during a sport event, [[Index term|keywords]] like ''goal'', ''red card'' will be associated to some clips)
* ''classify'' media: metadata allows producers to sort the media or to easily and quickly find a video content (a TV news could urgently need some archive content for a subject). For example, the BBC has a large subject classification system, [[Lonclass]], a customized version of the more general-purpose [[Universal Decimal Classification]].

This metadata can be linked to the video media thanks to the [[Engineering:Video server#Broadcast automation|video servers]]. Most major broadcast sporting events like FIFA World Cup or the [[Social:Olympic Games|Olympic Games]] use this metadata to distribute their video content to TV stations through [[Index term|keywords]]. It is often the host broadcaster<ref>{{cite web |url=http://www.hbs.tv/hostbroadcasting/ |title=HBS is the FIFA host broadcaster |publisher=Hbs.tv |date=6 August 2011 |access-date=23 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120117194534/http://www.hbs.tv/hostbroadcasting/ |archive-date=17 January 2012}}</ref> who is in charge of organizing metadata through its ''International Broadcast Centre'' and its video servers. This metadata is recorded with the images and entered by metadata operators (''loggers'') who associate in live metadata available in ''metadata grids'' through [[Software|software]] (such as Multicam(LSM) or [[Engineering:IPDirector|IPDirector]] used during the FIFA World Cup or Olympic Games).<ref>{{cite web |url=http://www.evs-global.com/01/MyDocuments/CS_BOB_EVScontributon_0808_ENG.pdf |title=Host Broadcast Media Server and Related Applications |access-date=17 August 2013 |url-status=dead |archive-url=https://web.archive.org/web/20111102235256/http://www.evs-global.com/01/MyDocuments/CS_BOB_EVScontributon_0808_ENG.pdf |archive-date=2 November 2011}}</ref><ref>{{cite web |url=http://broadcastengineering.com/worldcup/fifa-world-cup-techonlogy-0610/ |title=logs during sport events |publisher=Broadcastengineering.com |access-date=23 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111116191929/http://broadcastengineering.com/worldcup/fifa-world-cup-techonlogy-0610/ |archive-date=16 November 2011}}</ref>

=== Geography ===
Metadata that describes geographic objects in electronic storage or format (such as datasets, maps, features, or documents with a geospatial component) has a history dating back to at least 1994. This class of metadata is described more fully on the [[Geospatial metadata|geospatial metadata]] article.

=== Ecology and environment ===
Ecological and environmental metadata is intended to document the "who, what, when, where, why, and how" of data collection for a particular study. This typically means which organization or institution collected the data, what type of data, which date(s) the data was collected, the rationale for the data collection, and the methodology used for the data collection. Metadata should be generated in a format commonly used by the most relevant science community, such as Darwin Core, [[Ecological Metadata Language]],<ref>{{cite web |url=http://knb.ecoinformatics.org/software/eml/eml-2.0.1/index.html |title=Ecological Metadata Language (EML) Specification |website=Ecoinformatics |access-date=16 July 2022 |archive-url=https://web.archive.org/web/20110423161141/http://knb.ecoinformatics.org/software/eml/eml-2.0.1/index.html |archive-date=23 April 2011}}</ref> or [[Dublin Core]]. Metadata editing tools exist to facilitate metadata generation (e.g. Metavist,<ref>{{cite web |url=http://metavist.djames.net/ |title=Metavist 2 |publisher=Metavist.djames.net |access-date=23 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110821202734/http://metavist.djames.net/ |archive-date=21 August 2011}}</ref> [[Mercury (metadata search system)|Mercury]], Morpho<ref>{{cite web |url=http://knb.ecoinformatics.org/morphoportal.jsp |title=KNB Data :: Morpho |publisher=Knb.ecoinformatics.org |date=20 May 2009 |access-date=23 December 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120113143228/http://knb.ecoinformatics.org/morphoportal.jsp |archive-date=13 January 2012}}</ref>). Metadata should describe the provenance of the data (where they originated, as well as any transformations the data underwent) and how to give credit for (cite) the data products.

=== Digital music ===
When first released in 1982, Compact Discs only contained a Table Of Contents (TOC) with the number of tracks on the disc and their length in samples.<ref>{{cite journal |url=https://journals.sagepub.com/doi/abs/10.1177/1461444811430645 |title=Making music behave: Metadata and the digital music commodity |last=Morris |first=Jeremy W |journal=New Media & Society |date=28 February 2012 |volume=14 |issue=5 |pages=850–866 |doi=10.1177/1461444811430645 |s2cid=42147222 |access-date=12 March 2023 |archive-url=https://web.archive.org/web/20210224051543/https://journals.sagepub.com/doi/abs/10.1177/1461444811430645 |archive-date=24 February 2021}}</ref><ref name="Pohlmann1989">{{cite book |first=Ken C. |last=Pohlmann |title=The Compact Disc: A Handbook of Theory and Use |url=https://archive.org/details/compactdischandb0000pohl |url-access=registration |year=1989 |publisher=A-R Editions, Inc. |isbn=978-0-89579-228-0 |pages=[https://archive.org/details/compactdischandb0000pohl/page/48 48]–}}</ref> Fourteen years later in 1996, a revision of the [[Company:Compact Disc Digital Audio|CD Red Book]] standard added [[CD-Text]] to carry additional metadata.<ref>{{Cite web |url=http://web.ncf.ca/aa571/cdtext.htm |title=Unofficial CD Text FAQ |website=Computall Services |access-date=16 July 2022 |archive-url=https://web.archive.org/web/20220408075911/http://web.ncf.ca/aa571/cdtext.htm |archive-date=8 April 2022}}</ref> But CD-Text was not widely adopted. Shortly thereafter, it became common for personal computers to retrieve metadata from external sources (e.g. CDDB, Gracenote) based on the TOC.

Digital [[Engineering:Sound recording and reproduction|audio]] formats such as digital audio files superseded music formats such as [[Engineering:Cassette tape|cassette tape]]s and CDs in the 2000s. Digital audio files could be labeled with more information than could be contained in just the file name. That descriptive information is called the '''audio tag''' or audio metadata in general. Computer programs specializing in adding or modifying this information are called [[Software:Tag editor|tag editor]]s. Metadata can be used to name, describe, catalog, and indicate ownership or copyright for a digital audio file, and its presence makes it much easier to locate a specific audio file within a group, typically through use of a search engine that accesses the metadata. As different digital audio formats were developed, attempts were made to standardize a specific location within the digital files where this information could be stored.

As a result, almost all digital audio formats, including mp3, broadcast wav, and AIFF files, have similar standardized locations that can be populated with metadata. The metadata for compressed and uncompressed digital music is often encoded in the [[ID3]] tag. Common editors such as [[Software:TagLib|TagLib]] support MP3, Ogg Vorbis, FLAC, MPC, Speex, WavPack TrueAudio, WAV, AIFF, MP4, and ASF file formats.

=== Cloud applications ===
With the availability of [[Cloud computing|cloud]] applications, which include those to add metadata to content, metadata is increasingly available over the Internet.

== Administration and management ==

=== Storage ===
Metadata can be stored either ''internally'',<ref name="id3">{{cite web |first=Dan |last=O'Neill |url=http://id3.org/ |title=ID3.org |url-status=dead |archive-url=https://web.archive.org/web/20111111055609/http://www.id3.org/ |archive-date=11 November 2011 |access-date=1 April 2020}}</ref> in the same file or structure as the data (this is also called ''embedded metadata''), or ''externally'', in a separate file or field from the described data. A data repository typically stores the metadata ''detached'' from the data but can be designed to support embedded metadata approaches. Each option has advantages and disadvantages:
* Internal storage means metadata always travels as part of the data they describe; thus, metadata is always available with the data, and can be manipulated locally. This method creates redundancy (precluding normalization), and does not allow managing all of a system's metadata in one place. It arguably increases consistency, since the metadata is readily changed whenever the data is changed.
* External storage allows collocating metadata for all the contents, for example in a database, for more efficient searching and management. Redundancy can be avoided by normalizing the metadata's organization. In this approach, metadata can be united with the content when information is transferred, for example in [[Engineering:Streaming media|Streaming media]]; or can be referenced (for example, as a web link) from the transferred content. On the downside, the division of the metadata from the data content, especially in standalone files that refer to their source metadata elsewhere, increases the opportunities for misalignments between the two, as changes to either may not be reflected in the other.

Metadata can be stored in either human-readable or binary form. Storing metadata in a human-readable format such as [[XML]] can be useful because users can understand and edit it without specialized tools.<ref name="Sutter">{{Cite book |first1=Robbie |last1=De Sutter |first2=Stijn |last2=Notebaert |first3=Rik |last3=Van de Walle |chapter=Evaluation of Metadata Standards in the Context of Digital Audio-Visual Libraries |title=Research and Advanced Technology for Digital Libraries: 10th European Conference, EDCL 2006 |editor1-last=Gonzalo |editor1-first=Julio |editor2-last=Thanos |editor2-first=Constantino |editor3-last=Verdejo |editor3-first=M. Felisa |editor4-last=Carrasco |editor4-first=Rafael |date=September 2006 |chapter-url=https://books.google.com/books?id=kU7Lqqowp54C&pg=PA226 |isbn=978-3-540-44636-1 |publisher=Springer |page=226 |url-status=live |archive-url=https://web.archive.org/web/20160427061113/https://books.google.com/books?id=kU7Lqqowp54C&pg=PA226&cad=4 |archive-date=27 April 2016}}</ref> However, text-based formats are rarely optimized for storage capacity, communication time, or processing speed. A binary metadata format enables efficiency in all these respects, but requires special software to convert the binary information into human-readable content.

=== Database management ===
Each relational database system has its own mechanisms for storing metadata. Examples of relational-database metadata include:
* Tables of all tables in a database, their names, sizes, and number of rows in each table.
* Tables of columns in each database, what tables they are used in, and the type of data stored in each column.
In database terminology, this set of metadata is referred to as the [[Database catalog|catalog]]. The [[SQL]] standard specifies a uniform means to access the catalog, called the [[Information schema|information schema]], but not all databases implement it, even if they implement other aspects of the SQL standard. For an example of database-specific metadata access methods, see [[Oracle metadata]]. Programmatic access to metadata is possible using APIs such as JDBC, or SchemaCrawler.<ref name="schemacrawler">{{cite web |first=Sualeh |last=Fatehi |url=http://schemacrawler.sourceforge.net/ |title=SchemaCrawler |work=SourceForge |url-status=live |archive-url=https://web.archive.org/web/20090903054127/http://schemacrawler.sourceforge.net/ |archive-date=3 September 2009}}</ref>

== Popular culture ==
One of the first satirical examinations of the concept of Metadata as we understand it today is American science fiction author [[Biography:Hal Draper|Hal Draper]]'s short story, "MS Fnd in a Lbry" (1961). Here, the knowledge of all Mankind is condensed into an object the size of a desk drawer, however, the magnitude of the metadata (e.g. catalog of catalogs of... , as well as indexes and histories) eventually leads to dire yet humorous consequences for the human race. The story prefigures the modern consequences of allowing metadata to become more important than the real data it is concerned with, and the risks inherent in that eventuality as a cautionary tale.

== See also ==
{{Div col|colwidth=25em}}
* {{annotated link|AGRIS}}
* {{annotated link|Biology:DataONE}}
* {{annotated link|Data dictionary}}
* {{annotated link|Dublin Core}}
* {{annotated link|Folksonomy}}
* {{annotated link|GEOMS – Generic Earth Observation Metadata Standard}}
* {{annotated link|Geospatial metadata}}
* {{annotated link|Engineering:IPDirector}}
* {{annotated link|Philosophy:The medium is the message}}
* {{annotated link|Meta element}}
* {{annotated link|IF-MAP|Metadata Access Point Interface}}
* {{annotated link|Metadata discovery}}
* {{annotated link|Metadata facility for Java}}
* {{annotated link|Metadata publishing}}
* {{annotated link|Metadata registry}}
* {{annotated link|Metamathematics}}
* {{annotated link|Earth:METAFOR}}
* {{annotated link|Microcontent}}
* {{annotated link|Microformat}}
* {{annotated link|Engineering:Multicam (LSM)}}
* {{annotated link|Observations and Measurements}}
* {{annotated link|Ontology (computer science)}}
* {{annotated link|Official statistics}}
* {{annotated link|Philosophy:Paratext}}
* {{annotated link|SDMX}}
* {{annotated link|Semantic Web}}
* {{annotated link|Universal Data Element Framework}}
* {{annotated link|Vocabulary OneSource}}
{{div col end}}

== References ==
{{Reflist}}

== Further reading ==
* {{wikicite|ref=|reference=Gartner, Richard. 2016. ''Metadata: Shaping Knowledge from Antiquity to the Semantic Web''. Springer. {{ISBN|9783319408910}}.}}
* {{wikicite|ref=|reference=Zeng, Marcia & Qin, Jian. 2016. ''Metadata''. Facet. {{ISBN|9781783300525}}.}}

== External links ==
* [https://web.archive.org/web/20170201234427/http://www.niso.org/apps/group_public/download.php/17446/Understanding%20Metadata ''Understanding Metadata: What is metadata, and what is it for?''] – NISO, 2017
* [https://web.archive.org/web/20140522165110/http://www.theguardian.com/technology/interactive/2013/jun/12/what-is-metadata-nsa-surveillance#meta=1111111 "A Guardian guide to your metadata"] – ''{{wipe|The Guardian}}'', Wednesday 12 June 2013.
* [http://www.well.com/~doctorow/metacrap.htm Metacrap: Putting the torch to 7 straw-men of the meta-utopia] – Cory Doctorow's opinion on the limitations of metadata on the [[Internet]], 2001
* [http://www.dataone.org/ DataONE] Investigator Toolkit
* [http://www.informaworld.com/openurl?genre=journal&issn=1938-6389 ''Journal of Library Metadata''], Routledge, Taylor & Francis Group, ISSN 1937-5034
* [http://www.inderscience.com/ijmso ''International Journal of Metadata, Semantics and Ontologies'' (''IJMSO'')], Inderscience Publishers, ISSN 1744-263X
* {{Cite web |url=https://washingtonindependent.com/_literature_52579/Stephen_Machin_–_ON_METADATA_AND_METACONTENT.pdf |title=Metadata and metacontent |access-date=25 June 2011}} (PDF)
* [https://www.dhs.gov/sites/default/files/publications/LPRStandards-TN_1012-508.pdf LPR Standards] (PDF), Department of Homeland Security (October 2012)

{{Software engineering}}
{{Data warehouse}}
{{Semantic Web}}

[[Category:Metadata| ]]
[[Category:Data management]]
[[Category:Knowledge representation]]
[[Category:Library cataloging and classification]]
[[Category:Records management]]
[[Category:Technical communication]]

{{Sourceattribution|Metadata}}