Quasi-identity
From Encyclopedia of Mathematics
conditional identity
Formulas of a first-order logical language of the form
 |
where 
and 
denote atomic formulas of the form
 |
where 
are terms in 
and 
is a primitive predicate symbol. Quasi-varieties of algebraic systems are defined by quasi-identities (cf. Algebraic systems, quasi-variety of). An identity is a special case of a quasi-identity.
Comments
Quasi-identities are also commonly called Horn sentences.
References
| [a1] | A. Horn, "On sentences which are true of direct unions of algebras" J. Symbol. Logic , 16 (1951) pp. 14–21 |
| [a2] | P.M. Cohn, "Universal algebra" , Reidel (1981) pp. 235 |
How to Cite This Entry:
Quasi-identity. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Quasi-identity&oldid=39459
Quasi-identity. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Quasi-identity&oldid=39459
This article was adapted from an original article by O.A. Ivanova (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article