View source for Structured entity relationship model

The '''SERM''' ('''structured entity relationship model''') is an amplification of the ERM which is commonly used for [[Data modeling|data modeling]]. It was first proposed from Prof. Dr. Elmar J. Sinz in 1988. The SERM is commonly used in the SAP-world for the [[Data modeling|data modeling]].<ref name="Röthlin2010">{{cite book|author=Michael Röthlin|title=Management of Data Quality in Enterprise Resource Planning Systems|url=https://books.google.com/books?id=wyheQllcyh0C&pg=PA118|year=2010|publisher=BoD – Books on Demand|isbn=978-3-89936-963-2|pages=118–}}</ref>

==Aims==
# structuring of large schemes 
# visualization of existence dependency
# avoidance of inconsistencies
# avoidance of unnecessary relationshiptypes

==SERM symbols==
[[Image:SERM-Symbols.JPG|600px]]

==SERM example==
[[Image:SERM-example.JPG]]

* Customer and article are independent entities
* Every order is referred to one customer. Orders without customers are illegal (order is an ER type). Customers without any orders are legal because they are independent Entities. 
* To every order there is belonging at least one order item. 
* Every order item is related to exactly one order. 
* Every invoice is referred to one customer, as well. Invoices without customers are illegal. Customers without any invoice are legal.
* To every invoice there is belonging at least one invoice line item.
* Every invoice line item is related to exactly order item. An order item could be calculated or not.
* SERM is already in the [[Third normal form|third normal form]]

==References==
{{reflist}}

[[Category:Data modeling]]
[[Category:Diagrams]]
[[Category:Modeling languages]]

{{Sourceattribution|Structured entity relationship model}}