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In abstract algebra, a partial algebra is a generalization of universal algebra to partial operations.[1][2]
There is a "Meta Birkhoff Theorem" by Andreka, Nemeti and Sain (1982).[1]
Operations and partial operations may be written as finitary relations, where there is no requirement of totality. "A relational system is a pair <A, R>, where A is a non-void set and R is a family of (finitary) relations on A."[2]: 8
Though relational systems have greater generality than algebras and partial algebras, they do not have the rich theory of the algebras.[4] For example, defining a subalgebra of a relational system is not straight forward.[5]