Quasiidentity

In universal algebra, a quasi-identity is an implication of the form

s₁ = t₁ ∧ … ∧ s_n = t_n → s = t

where s₁, ..., s_n, s and t₁, ..., t_n,t are terms built up from variables using the operation symbols of the specified signature.

Quasi-identities amount to conditional equations for which the conditions themselves are equations. A quasi-identity for which n = 0 is an ordinary identity or equation, whence quasi-identities are a generalization of identities. Quasi-identities are special type of Horn clauses.

See also

Quasivariety

References

• Burris, Stanley N.; H.P. Sankappanavar (1981). A Course in Universal Algebra. Springer. ISBN 3-540-90578-2.  Free online edition.