Essential variables and positions in terms
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The paper deals with Σ-composition of terms, which allows us to extend the derivation rules in formal deduction of identities. The concepts of essential variables and essential positions of terms with respect to a set of identities form a key step in the simplification of the process of formal deduction. Σ-composition of terms is defined as replacement between Σ-equal terms. This composition induces ΣR-deductively closed sets of identities. In analogy to balanced identities we introduce and investigate Σ-balanced identities for a given set of identities Σ.
2000 Mathematics Subject Classification08B05 08A02 03C05 08B15
Key words and phrasesComposition of terms essential position in a term globally invariant congruence stable variety
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