منابع مشابه
Expressibility in Σ
Inspired by Fagin’s result that NP = Σ 1 , we have developed a partial framework to investigate expressibility inside Σ 1 so as to have a finer look into NP . The framework uses interesting combinatorics derived from second-order EhrenfeuchtFräıssé games and the notion of game types. Some of the results that have been proven within this framework are: (1) for any k, divisibility by k is not exp...
متن کاملExpressibility and Parallel Complexity
It is shown that the time needed by a concurrent read concurrent write parallel random access machine CRAM to check if an input has a certain property is the same as the minimal depth of a rst order inductive de nition of the property This in turn is equal to the number of iterations of a rst order sentence needed to express the property The second contribution of this paper is the introduction...
متن کاملExpressibility of Properties of Relations
We investigate in an algebraic setting the question in which logical languages the properties integral, permutational, and rigid of algebras of relations can be expressed.
متن کاملExpressibility of Valued Constraints
In this paper we present a project on the expressibility of valued constraints. We recall the result of Cohen et al. [2] which characterises the expressibility of valued constraints in terms of algebraic properties of the constraints. We show why the current algebraic characterisation is rather unsatisfactory and what are the ways we try to explore in order to find a better one.
متن کاملExpressibility in Σ 11
Inspired by Fagin’s result that NP = Σ11, we have developed a partial framework to investigate expressibility inside Σ11 so as to have a finer look into NP . The framework uses interesting combinatorics derived from second-order Ehrenfeucht-Fräıssé games and the notion of game types. Some of the results that have been proven within this framework are: (1) for any k, divisibility by k is not exp...
متن کاملTesting Expressibility Is Hard
We study the expressibility problem: given a finite constraint language Γ on a finite domain and another relation R, can Γ express R? We prove, by an explicit family of examples, that the standard witnesses to expressibility and inexpressibility (gadgets/formulas/conjunctive queries and polymorphisms respectively) may be required to be exponentially larger than the instances. We also show that ...
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عنوان ژورنال:
فلسفهجلد ۳۵، شماره ۳، صفحات ۰-۰
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