By Hajnal Andreka, Steven R. Givant, Istvan Nemeti

This paintings provides a scientific examine of determination difficulties for equational theories of algebras of binary relatives (relation algebras). for instance, an simply acceptable yet deep approach, in accordance with von Neumann's coordinatization theorem, is built for constructing undecidability effects. the strategy is used to clear up numerous amazing difficulties posed by means of Tarski. furthermore, the complexity of durations of equational theories of relation algebras with recognize to questions of decidability is investigated. utilizing rules that return to Jónsson and Lyndon, the authors express that such durations may have a similar complexity because the lattice of subsets of the set of the normal numbers. ultimately, a few new and rather attention-grabbing examples of decidable equational theories are given.

The equipment built within the monograph exhibit promise of wide applicability. they supply researchers in algebra and good judgment with a brand new arsenal of options for resolving selection questions in quite a few domain names of algebraic good judgment.

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Proposition NoMatch2;(0 is true whenever the above partial function has no result. The next two rules start reducing the next argument of a partially applied variable or constant, when no reduction is possible. This is achieved by simply swapping the head and the argument (and @i becomes @R). The last rule applies when this argument has been weakly normalized, in which case it is applied to the head appearing in the stack. S) --^ (\-b = b',@R{ha = w h e n NoMatchi:(c w) --^ (ht = a' b',S) w h e n b' Wnf Fig.

Qm Qi ... Qi-i R "' C H-)> Q^+i ... Q^ C where 1 < i < »^ The proof term of the new proof state is obtained by supplying a suitable projection function as an argument to R: Ag~I- R Wl ( ^ ^ P^- Pi) Lifting rules into a context Before a subgoal of a proof state can be refined by resolution with a certain rule, the context of both the premises and the conclusion of this rule has to be augmented with additional parameters and assumptions in order to be compatible with the context of the subgoal. This process is called lifting.

HOL's reduceLib library was designed to (among others) avoid this problem and allow to compute efficiently usual boolean and numerical expressions. However, this mechanism is not general in the sense that it cannot deal with other user-defined constants, and the same effort will have to be done whenever we introduce constants such as datatype destructors. Consider for instance the option type. In the expression opt ion_case e f (SOME x ) , which reduces to f x, we would like to avoid computing the canonical form of e (the case for NONE).

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