谱有限或余有限的Bernays-Schönfinkel-Ramsey类的语义推广
On Semantic Generalizations of the Bernays-Schönfinkel-Ramsey Class with Finite or Co-finite Spectra
摘要:
基于BSR类的模型理论性质,我们提出了一个家庭的语义类的FO公式与有限或有限的频谱上的关系词汇表。这个族中的一个类记为EBS_n(σ),其中σ是n的子集。EBS_n(σ)中的公式在模有界核的子结构和对σ外谓词的模重解释下保持不变。本文研究了一族EBS_∞ = {EBS_∞(σ)}的性质|σ \subseteq n},例如EBS_n中的类在谱上是不可区分的,EBS_n(n)在语义上等价于n上的BSR,并且EBS_n(\emptyset)是n上具有有限或余有限谱的所有FO公式的集合。此外,(EBS_n,\subseteq)形成与幂集格(\wp(n),\subseteq)同构的格。这给出了将BSR自然语义概括为(EBS_REQ,\subseteq)中的上升链。许多著名的FO类在语义上都包含在EBS_LOG(LOG)或EBS_LOG(\emptyset)中。我们的研究提供了替代证明有趣的结果,如Lojan-Tarski定理和语义包容的Löwenheim类与平等的BSR。我们还提出了EBS_n(σ)的一个语法子类EDP_n(σ),并给出了EDP_n(σ)公式模型的有界核大小的表达式。我们证明了EDP_n(σ)类也形成格结构。最后,我们研究了所提出的类的一些闭包性质和应用。
英文摘要:
Motivated by model-theoretic properties of the BSR class, we present a family of semantic classes of FO formulae with finite or co-finite spectra over a relational vocabulary Σ. A class in this family is denoted EBS_Σ(σ), where σis a subset of Σ. Formulae in EBS_Σ(σ) are preserved under substructures modulo a bounded core and modulo re-interpretation of predicates outside σ. We study properties of the family EBS_Σ= {EBS_Σ(σ) | σ\subseteq Σ}, e.g. classes in EBS_Σare spectrally indistinguishable, EBS_Σ(Σ) is semantically equivalent to BSR over Σ, and EBS_Σ(\emptyset) is the set of all FO formulae over Σwith finite or co-finite spectra. Furthermore, (EBS_Σ, \subseteq) forms a lattice isomorphic to the powerset lattice (\wp(Σ), \subseteq). This gives a natural semantic generalization of BSR as ascending chains in (EBS_Σ, \subseteq). Many well-known FO classes are semantically subsumed by EBS_Σ(Σ) or EBS_Σ(\emptyset). Our study provides alternative proofs of interesting results like the Loś-Tarski Theorem and the semantic subsumption of the Löwenheim class with equality by BSR. We also present a syntactic sub-class of EBS_Σ(σ) called EDP_Σ(σ) and give an expression for the size of the bounded cores of models of EDP_Σ(σ) formulae. We show that the EDP_Σ(σ) classes also form a lattice structure. Finally, we study some closure properties and applications of the classes presented.
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