Predicate Symbols Research Articles

Algorithm for Extraction Common Properties of Objects Described in the Predicate Calculus Language with Several Predicate Symbols

Algorithm for Extraction Common Properties of Objects Described in the Predicate Calculus Language with Several Predicate Symbols

A Decidable Fragment of First Order Modal Logic: Two Variable Term Modal Logic

First order modal logic (𝖥𝖮𝖬𝖫) is built by extending First Order Logic (𝖥𝖮) with modal operators. A typical formula is of the form \(\forall x \exists y \Box P(x,y)\) . Not only is 𝖥𝖮𝖬𝖫 undecidable, even simple fragments like that of restriction to unary predicate symbols, guarded fragment and two variable fragment, which are all decidable for 𝖥𝖮 become undecidable for 𝖥𝖮𝖬𝖫. In this paper we study Term Modal logic (𝖳𝖬𝖫) which allows modal operators to be indexed by terms. A typical formula is of the form \(\forall x \exists y~\Box _x P(x,y)\) . There is a close correspondence between 𝖳𝖬𝖫 and 𝖥𝖮𝖬𝖫 and we explore this relationship in detail in the paper. In contrast to 𝖥𝖮𝖬𝖫, we show that the two variable fragment (without constants, equality) of 𝖳𝖬𝖫 is decidable. Further, we prove that adding a single constant makes the two variable fragment of 𝖳𝖬𝖫 undecidable. On the other hand, when equality is added to the logic, it loses the finite model property.

SAT-Inspired Higher-Order Eliminations

We generalize several propositional preprocessing techniques to higher-order logic, building on existing first-order generalizations. These techniques eliminate literals, clauses, or predicate symbols from the problem, with the aim of making it more amenable to automatic proof search. We also introduce a new technique, which we call quasipure literal elimination, that strictly subsumes pure literal elimination. The new techniques are implemented in the Zipperposition theorem prover. Our evaluation shows that they sometimes help prove problems originating from Isabelle formalizations and the TPTP library.

The undecidability of proof search when equality is a logical connective

One proof-theoretic approach to equality in quantificational logic treats equality as a logical connective: in particular, term equality can be given both left and right introduction rules in a sequent calculus proof system. We present a particular example of this approach to equality in a first-order logic setting in which there are no predicate symbols (apart from equality). After we illustrate some interesting applications of this logic, we show that provability in this logic is undecidable.

Exorcising the phantom zone

In this paper we introduce a language of first-order hybrid logic in which function symbols are interpreted by partial functions and prove a number of completeness results. Syntactically, our language builds on the basic propositional hybrid language, has a primitive unary predicate symbol DEN which tests whether a term denotes or not, and permits satisfaction operators to rigidify predicate and function symbols. Semantically, our system is actualist, allows terms to be undefined, and has no truth-value gaps. But should we follow Fitting and Mendelsohn and rule out domain elements not belonging to any world, or should we tolerate them? Here we explore both options. As we shall see, while the choice makes no difference when it comes to validity, it has consequences for richer logics.

Towards the entropy-limit conjecture

The maximum entropy principle is widely used to determine non-committal probabilities on a finite domain, subject to a set of constraints, but its application to continuous domains is notoriously problematic. This paper concerns an intermediate case, where the domain is a first-order predicate language. Two strategies have been put forward for applying the maximum entropy principle on such a domain: (i) applying it to finite sublanguages and taking the pointwise limit of the resulting probabilities as the size n of the sublanguage increases; (ii) selecting a probability function on the language as a whole whose entropy on finite sublanguages of size n is not dominated by that of any other probability function for sufficiently large n. The entropy-limit conjecture says that, where these two approaches yield determinate probabilities, the two methods yield the same probabilities. If this conjecture is found to be true, it would provide a boost to the project of seeking a single canonical inductive logic—a project which faltered when Carnap's attempts in this direction succeeded only in determining a continuum of inductive methods. The truth of the conjecture would also boost the project of providing a canonical characterisation of normal or default models of first-order theories.Hitherto, the entropy-limit conjecture has been verified for languages which contain only unary predicate symbols and also for the case in which the constraints can be captured by a categorical statement of Σ1 quantifier complexity. This paper shows that the entropy-limit conjecture also holds for categorical statements of Π1 complexity, for various non-categorical constraints, and in certain other general situations.

Decidable $${\exists }^*{\forall }^*$$ First-Order Fragments of Linear Rational Arithmetic with Uninterpreted Predicates

First-order linear rational arithmetic enriched with uninterpreted predicates yields an interesting and very expressive modeling language. However, already the presence of a single uninterpreted predicate symbol of arity one or greater renders the associated satisfiability problem undecidable. We identify two decidable fragments, both based on the Bernays–Schonfinkel–Ramsey prefix class. Due to the inherent infiniteness of the underlying domain, a finite model property in the usual sense cannot be established. Nevertheless, we show that satisfiable sentences always have a model that can be described by finite means. To this end, we restrict the syntax of arithmetic atoms. In the first fragment that is presented, arithmetic operations are only allowed over terms without universally quantified variables. In the second fragment, arithmetic atoms are essentially confined to difference constraints over universally quantified variables with bounded range. We will call such atoms bounded difference constraints. As bounded intervals over the rationals still comprise infinitely many values, a trivial instantiation procedure is not sufficient to solve the satisfiability problem. After a slight shift of perspective, the positive decidability result for the first fragment can be restated in the framework of combinations of theories over non-disjoint vocabularies. More precisely, we combine first-order theories that share a dense total order without endpoints.

The Bernays-Schönfinkel-Ramsey Class of Separation Logic with Uninterpreted Predicates

This article investigates the satisfiability problem for Separation Logic with k record fields, with unrestricted nesting of separating conjunctions and implications. It focuses on prenex formulæ with a quantifier prefix in the language ∃*∀* that contain uninterpreted (heap-independent) predicate symbols. In analogy with first-order logic, we call this fragment Bernays-Schönfinkel-Ramsey Separation Logic [BSR(SL k )]. In contrast with existing work on Separation Logic, in which the universe of possible locations is assumed to be infinite, we consider both finite and infinite universes in the present article. We show that, unlike in first-order logic, the (in)finite satisfiability problem is undecidable for BSR(SL k ). Then we define two non-trivial subsets thereof, for which the finite and infinite satisfiability problems are PSPACE-complete, respectively, assuming that the maximum arity of the uninterpreted predicate symbols does not depend on the input. These fragments are defined by controlling the polarity of the occurrences of separating implications, as well as the occurrences of universally quantified variables within their scope. These decidability results have natural applications in program verification, as they allow to automatically prove lemmas that occur in, e.g., entailment checking between inductively defined predicates and validity checking of Hoare triples expressing partial correctness conditions.

On the complexity of index sets for finite predicate logic programs which allow function symbols

AbstractWe study the recognition problem in the metaprogramming of finite normal predicate logic programs. That is, let $\mathcal{L}$ be a computable first-order predicate language with infinitely many constant symbols and infinitely many $n$-ary predicate symbols and $n$-ary functions symbols for all $n \geq 1$. Then we can effectively list all the finite normal predicate logic programs $Q_0,Q_1,\ldots $ over $\mathcal{L}$. Given some property $\mathcal{P}$ of finite normal predicate logic programs over $\mathcal{L}$, we define the index set $I_{\mathcal{P}}$ to be the set of indices $e$ such that $Q_e$ has property $\mathcal{P}$. We classify the complexity of the index set $I_{\mathcal{P}}$ within the arithmetic hierarchy for various natural properties of finite predicate logic programs. For example, we determine the complexity of the index sets relative to all finite predicate logic programs and relative to certain special classes of finite predicate logic programs of properties such as (i) having no stable models, (ii) having no recursive stable models, (iii) having at least one stable model, (iv) having at least one recursive stable model, (v) having exactly $c$ stable models for any given positive integer $c$, (vi) having exactly $c$ recursive stable models for any given positive integer $c$, (vii) having only finitely many stable models, (viii) having only finitely many recursive stable models, (ix) having infinitely many stable models and (x) having infinitely many recursive stable models.

Тезис Пирса: логический анализ и онтологические следствия


 Ч.С. Пирс выдвинул гипотезу о том, что любые отношения могут быть редуцированы к отношениям, местность которых не превышает трех. Эта гипотеза тесно связана с базовыми категориями его феноменологии.
 
 В данной публикации дан семантический анализ и подробное доказательство следующих двух результатов. 
 
 1. Любая первопорядковая теория может быть представлена в языке, содержащем конечный набор одноместных функциональных символов. Философски важным следствием этого является равноправие реляционных и функциональных языков и соответствующих им онтологий. 
 
 2. Любая первопорядковая теория может быть представлена в языке, содержащем единственный трехместный предикатный символ $ U $ и конечный набор индивидных констант. Это подтверждает гипотезу Пирса о фундаментальной роли, которую играют трехместные отношения. Язык, дескриптивные символы которого содержат лишь индивидные константы и единственный трехместный предикат, оказывается универсальным языком для представления любых теорий первого порядка. 
 
 Имеется структурное сходство трехместного предиката $ U(e,u,x) $ и трехместного предиката $ UM(e,u,x) $, представляющего универсальную машину Тьюринга. И тот и другой можно рассматривать как контейнеры одноместных функций. С этой точки зрения предикат $ U $ является расширением предиката $ UM $ на любые, а не только эффективно вычислимые функции.
 
 Доказанные теоремы заставляют по-новому взглянуть на многие физические теории. В теории относительности фундаментальной структурой считается четырехмерное пространство-время Минковского, которое можно представить в виде четырехместного предиката $ S(x,y,z,t) $. Из теоремы о существовании предиката $ U(e,u,x) $ следует, что четырехмерное пространство-время Минковского не является фундаментальной физической структурой, поскольку может быть редуцировано к единственному трехместному отношению.
 

Concrete barriers to quantifier elimination in finite dimensional C*‐algebras

AbstractWork of Eagle, Farah, Goldbring, Kirchberg, and Vignati shows that the only separable C*‐algebras that admit quantifier elimination in continuous logic are , , , and the continuous functions on the Cantor set. We show that, among finite dimensional C*‐algebras, quantifier elimination does hold if the language is expanded to include two new predicate symbols: One for minimal projections, and one for pairs of unitarily conjugate elements. Both of these predicates are definable, but not quantifier‐free definable, in the usual language of C*‐algebras. We also show that adding just the predicate for minimal projections is sufficient in the case of full matrix algebras, but that in general both new predicate symbols are required.

ON A QUESTION OF KRAJEWSKI’S

AbstractIn this paper, we study finitely axiomatizable conservative extensions of a theoryUin the case whereUis recursively enumerable and not finitely axiomatizable. Stanisław Krajewski posed the question whether there are minimal conservative extensions of this sort. We answer this question negatively.Consider a finite expansion of the signature ofUthat contains at least one predicate symbol of arity ≥ 2. We show that, for any finite extensionαofUin the expanded language that is conservative overU, there is a conservative extensionβofUin the expanded language, such that$\alpha \vdash \beta$and$\beta \not \vdash \alpha$. The result is preserved when we consider eitherextensionsormodel-conservative extensionsofUinstead ofconservative extensions. Moreover, the result is preserved when we replace$\dashv$as ordering on the finitely axiomatized extensions in the expanded language by a relevant kind of interpretability, to witinterpretability that identically translates the symbols of the U-language.We show that the result fails when we consider an expansion with only unary predicate symbols for conservative extensions ofUordered by interpretability that preserves the symbols ofU.

Towards Combining Model Checking and Proof Checking

Model checking and automated theorem proving are two pillars of formal verification methods. This paper investigates model checking from an automated theorem proving perspective, aiming at combining the expressiveness of automated theorem proving and the complete automaticity of model checking. It places the focus on the verification of temporal logic properties of Kripke models. The main contributions are: (1) introducing an extended computation tree logic that allows polyadic predicate symbols; (2) designing a proof system for this logic, taking Kripke models as parameters; (3) developing a proof search algorithm for this system and a new automated theorem prover to implement it. The verification process of the new prover is completely automatic, and produces either a counterexample when the property does not hold, or a certificate when it does. The experimental results compare well to existing state-of-the-art tools on some benchmarks, and the efficiency is illustrated by application to an air traffic control problem.

Propositional Epistemic Logics with Quantification Over Agents of Knowledge (An Alternative Approach)

In the previous paper with a similar title (see Shtakser in Stud Log 106(2):311–344, 2018), we presented a family of propositional epistemic logics whose languages are extended by two ingredients: (a) by quantification over modal (epistemic) operators or over agents of knowledge and (b) by predicate symbols that take modal (epistemic) operators (or agents) as arguments. We denoted this family by $${\mathcal {P}\mathcal {E}\mathcal {L}}_{(QK)}$$ . The family $${\mathcal {P}\mathcal {E}\mathcal {L}}_{(QK)}$$ is defined on the basis of a decidable higher-order generalization of the loosely guarded fragment (HO-LGF) of first-order logic. And since HO-LGF is decidable, we obtain the decidability of logics of $${\mathcal {P}\mathcal {E}\mathcal {L}}_{(QK)}$$ . In this paper we construct an alternative family of decidable propositional epistemic logics whose languages include ingredients (a) and (b). Denote this family by $${\mathcal {P}\mathcal {E}\mathcal {L}}^{alt}_{(QK)}$$ . Now we will use another decidable fragment of first-order logic: the two variable fragment of first-order logic with two equivalence relations (FO $$^2$$ +2E) [the decidability of FO $$^2$$ +2E was proved in Kieronski and Otto (J Symb Log 77(3):729–765, 2012)]. The families $${\mathcal {P}\mathcal {E}\mathcal {L}}^{alt}_{(QK)}$$ and $${\mathcal {P}\mathcal {E}\mathcal {L}}_{(QK)}$$ differ in the expressive power. In particular, we exhibit classes of epistemic sentences considered in works on first-order modal logic demonstrating this difference.

The Atomic Theory of Division and Intersection of Semiring Ideals

We consider two-sided ideals of semirings. More precisely, we study the theory of two-sided ideals in the signature consisting of the predicate symbol ⊆ and three function symbols that denote the intersection, right division, and left division of ideals. We prove the decidability of the set of those atomic formulas in this signature that are valid for all semirings and all valuations.

The Substitutional Analysis of Logical Consequence

AbstractA substitutional account of logical validity for formal first‐order languages is developed and defended against competing accounts such as the model‐theoretic definition of validity. Roughly, a substitution instance of a sentence is defined as the result of uniformly substituting nonlogical expressions in the sentence with expressions of the same grammatical category and possibly relativizing quantifiers. In particular, predicate symbols can be replaced with formulae possibly containing additional free variables. A sentence is defined to be logically true iff all its substitution instances are satisfied by all variable assignments. Logical consequence is defined analogously. Satisfaction is taken to be a primitive notion and axiomatized.For every set‐theoretic model in the sense of model theory there exists a corresponding substitutional interpretation in a sense to be specified. Conversely, however, there are substitutional interpretations – in particular the ‘intended’ interpretation – that lack a model‐theoretic counterpart. The substitutional definition of logical validity overcomes the weaknesses of more restrictive accounts of substitutional validity; unlike model‐theoretic logical consequence, the substitutional notion is trivially and provably truth preserving. In Kreisel's squeezing argument the formal notion of substitutional validity naturally slots into the place of intuitive validity.

Ultra-Strong Machine Learning: comprehensibility of programs learned with ILP

During the 1980s Michie defined Machine Learning in terms of two orthogonal axes of performance: predictive accuracy and comprehensibility of generated hypotheses. Since predictive accuracy was readily measurable and comprehensibility not so, later definitions in the 1990s, such as Mitchell’s, tended to use a one-dimensional approach to Machine Learning based solely on predictive accuracy, ultimately favouring statistical over symbolic Machine Learning approaches. In this paper we provide a definition of comprehensibility of hypotheses which can be estimated using human participant trials. We present two sets of experiments testing human comprehensibility of logic programs. In the first experiment we test human comprehensibility with and without predicate invention. Results indicate comprehensibility is affected not only by the complexity of the presented program but also by the existence of anonymous predicate symbols. In the second experiment we directly test whether any state-of-the-art ILP systems are ultra-strong learners in Michie’s sense, and select the Metagol system for use in humans trials. Results show participants were not able to learn the relational concept on their own from a set of examples but they were able to apply the relational definition provided by the ILP system correctly. This implies the existence of a class of relational concepts which are hard to acquire for humans, though easy to understand given an abstract explanation. We believe improved understanding of this class could have potential relevance to contexts involving human learning, teaching and verbal interaction.

Модель целеполагания в многоагентной системе с ограниченным ресурсом времени

The article considers the goal-setting model concept in modeling the reasoning of cognitive agents in dynamic hard real-time systems. An important issue concerned with processing tasks by means of hard real-time systems is the ability to estimate the amount of time available for processing till the moment of time it becomes too late to produce the result. To avoid such a situation, it is necessary to be able to correlate the steps and results of ongoing reasoning with the events occurring in the external environment. Reasoning of this type is called reasoning in time. To formalize such reasoning, formalisms of active logic are suggested. When regarded as a deduction model, active logic is characterized by a language and a set of deductive rules and observations. By using an observation function, one can model a dynamic environment, information about which arrives to the agent as changes occur in that environment. Reasoning in time is characterized by accomplishment of deduction cycles (steps) serving as a time standard. The agent's knowledge is associated with the index of the step on which it was gained for the first time. Observations can be carried out at any step of the deductive process, and a formula expressing some statement and associated with the relevant step serves as its result. To construct a goal-setting model for solving problems in hard real-time environment, a logic system (a metalogic of knowledge) is introduced to formalize in the general case the metareasoning of several intellectual agents about the tasks they face, about their own knowledge, and about the possibilities of solving these problems in interaction with the other agents, taking into account the limited time resource available to each of the agents. The goal-setting process gives an answer to the question of which subgoals and in what sequence at a given moment in time should be achieved for the main goal faced by the multi-agent system be fulfilled within acceptable time. It should be noted that the response may vary depending on the current situation and as additional information becomes available, because the assigned targets may be canceled and new ones assigned. The knowledge metalogics language is shown as a combination of three languages: the language of problem domain, the language of agents, and metalanguage, with the last two being multigrade ones. The language of agents contains special predicate symbols for reasoning about goals, about the tasks associated with them, about the structure of these tasks, and about possible methods and admissible timeframes for solving them. Metalanguage allows one to express general statements about the arguments of agents. Formal theories constituting the meta-knowledge system of knowledge are presented.

Propositional Epistemic Logics with Quantification Over Agents of Knowledge

The paper presents a family of propositional epistemic logics such that languages of these logics are extended by quantification over modal (epistemic) operators or over agents of knowledge and extended by predicate symbols that take modal (epistemic) operators (or agents) as arguments. Denote this family by \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\). There exist epistemic logics whose languages have the above mentioned properties (see, for example Corsi and Orlandelli in Stud Log 101:1159–1183, 2013; Fitting et al. in Stud Log 69:133–169, 2001; Grove in Artif Intell 74(2):311–350, 1995; Lomuscio and Colombetti in Proceedings of ATAL 1996. Lecture Notes in Computer Science (LNCS), vol 1193, pp 71–85, 1996). But these logics are obtained from first-order modal logics, while a logic of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) can be regarded as a propositional multi-modal logic whose language includes quantifiers over modal (epistemic) operators and predicate symbols that take modal (epistemic) operators as arguments. Among the logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) there are logics with a syntactical distinction between two readings of epistemic sentences: de dicto and de re (between ‘knowing that’ and ‘knowing of’). We show the decidability of logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) with the help of the loosely guarded fragment (LGF) of first-order logic. Namely, we generalize LGF to a higher-order decidable loosely guarded fragment. The latter fragment allows us to construct various decidable propositional epistemic logics with quantification over modal (epistemic) operators. The family of this logics coincides with \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\). There are decidable propositional logics such that these logics implicitly contain quantification over agents of knowledge, but languages of these logics are usual propositional epistemic languages without quantifiers and predicate symbols (see Grove and Halpern in J Log Comput 3(4):345–378, 1993). Some logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) can be regarded as counterparts of logics defined in Grove and Halpern (J Log Comput 3(4):345–378, 1993). We prove that the satisfiability problem for these logics of \({\mathcal {P}\mathcal {E}\mathcal {L}}_{({ QK})}\) is Pspace-complete using their counterparts in Grove and Halpern (J Log Comput 3(4):345–378, 1993).

A Complete Uniform Substitution Calculus for Differential Dynamic Logic

This article introduces a relatively complete proof calculus for differential dynamic logic (dL) that is entirely based on uniform substitution, a proof rule that substitutes a formula for a predicate symbol everywhere. Uniform substitutions make it possible to use axioms instead of axiom schemata, thereby substantially simplifying implementations. Instead of subtle schema variables and soundness-critical side conditions on the occurrence patterns of logical variables to restrict infinitely many axiom schema instances to sound ones, the resulting calculus adopts only a finite number of ordinary dLformulas as axioms, which uniform substitutions instantiate soundly. The static semantics of differential dynamic logic and the soundness-critical restrictions it imposes on proof steps is captured exclusively in uniform substitutions and variable renamings as opposed to being spread in delicate ways across the prover implementation. In addition to sound uniform substitutions, this article introduces differential forms for differential dynamic logic that make it possible to internalize differential invariants, differential substitutions, and derivatives as first-class axioms to reason about differential equations axiomatically. The resulting axiomatization of differential dynamic logic is proved to be sound and relatively complete.