The measure quantifier

1979 ◽  
Vol 44 (1) ◽  
pp. 103-108 ◽  
Author(s):  
Carl F. Morgenstern
Keyword(s):  
Measurable Cardinal ◽  
Order Logic ◽  
First Order Logic ◽  
Order Structure ◽  
Proper Class ◽  
First Order ◽  
Recursive Enumerability ◽  
Almost All ◽  
Measurable Cardinals ◽  
The Universe

Originally generalized quantifiers were introduced to specify that a given formula was true for “many x's” e.g. ⊨ Qxφ(x) iff card{x ∈ ∣∣ ∣ ⊨ φ[x]} ≥ ℵ0, ℵ1, or some fixed cardinal κ. In this paper we formalize the notion that φ{x) is true “for almost all x”. This is accomplished by referring to structures = (′, μ) where ′ is a first-order structure and μ is a measure of a suitable type on the universe of ′. We will prove that the language Lμ obtained from first-order logic by adjoining a quantifier Qμ, which ranges over the measure μ, is fully compact if we assume the existence of a proper class of measurable cardinals. As a corollary to the compactness theorem we obtain the recursive enumerability of the validities of Lμ. Finally, the Magidor-Malitz quantifiers Qkn (n ∈ ω) will be added to Lμ together with analogous quantifiers Qμm (m ∈ ω) to form Lκμ<ω,<ω, which is compact for sets of sentences of cardinality < κ, where κ is a measurable cardinal > ℵ0.An alternate approach to formalizing “for almost all” has been recently developed by Barwise, Kaufmann and Makkai [1] who follow a suggestion of Shelah [5].

μ-definable sets of integers

1993 ◽  
Vol 58 (1) ◽  
pp. 291-313 ◽  
Author(s):  
Robert S. Lubarsky
Keyword(s):  
Fixed Point ◽  
Free Variable ◽  
Order Logic ◽  
First Order Logic ◽  
Inductive Definition ◽  
Natural Class ◽  
First Order ◽  
Inductive Definitions ◽  
Definable Sets ◽  
The Universe

Inductive definability has been studied for some time already. Nonetheless, there are some simple questions that seem to have been overlooked. In particular, there is the problem of the expressibility of the μ-calculus.The μ-calculus originated with Scott and DeBakker [SD] and was developed by Hitchcock and Park [HP], Park [Pa], Kozen [K], and others. It is a language for including inductive definitions with first-order logic. One can think of a formula in first-order logic (with one free variable) as defining a subset of the universe, the set of elements that make it true. Then “and” corresponds to intersection, “or” to union, and “not” to complementation. Viewing the standard connectives as operations on sets, there is no reason not to include one more: least fixed point.There are certain features of the μ-calculus coming from its being a language that make it interesting. A natural class of inductive definitions are those that are monotone: if X ⊃ Y then Γ (X) ⊃ Γ (Y) (where Γ (X) is the result of one application of the operator Γ to the set X). When studying monotonic operations in the context of a language, one would need a syntactic guarantor of monotonicity. This is provided by the notion of positivity. An occurrence of a set variable S is positive if that occurrence is in the scopes of exactly an even number of negations (the antecedent of a conditional counting as a negation). S is positive in a formula ϕ if each occurrence of S is positive. Intuitively, the formula can ask whether x ∊ S, but not whether x ∉ S. Such a ϕ can be considered an inductive definition: Γ (X) = {x ∣ ϕ(x), where the variable S is interpreted as X}. Moreover, this induction is monotone: as X gets bigger, ϕ can become only more true, by the positivity of S in ϕ. So in the μ-calculus, a formula is well formed by definition only if all of its inductive definitions are positive, in order to guarantee that all inductive definitions are monotone.

Second- and higher-order logics

2018 ◽  
Author(s):  
Shaughan Lavine
Keyword(s):  
Predicate Logic ◽  
Higher Order ◽  
Second Order ◽  
Order Logic ◽  
First Order Logic ◽  
Third Order ◽  
First Order ◽  
Proof Systems ◽  
The Universe ◽  
Second Order Logic

In first-order predicate logic there are symbols for fixed individuals, relations and functions on a given universe of individuals and there are variables ranging over the individuals, with associated quantifiers. Second-order logic adds variables ranging over relations and functions on the universe of individuals, and associated quantifiers, which are called second-order variables and quantifiers. Sometimes one also adds symbols for fixed higher-order relations and functions among and on the relations, functions and individuals of the original universe. One can add third-order variables ranging over relations and functions among and on the relations, functions and individuals on the universe, with associated quantifiers, and so on, to yield logics of even higher order. It is usual to use proof systems for higher-order logics (that is, logics beyond first-order) that include analogues of the first-order quantifier rules for all quantifiers. An extensional n-ary relation variable in effect ranges over arbitrary sets of n-tuples of members of the universe. (Functions are omitted here for simplicity: remarks about them parallel those for relations.) If the set of sets of n-tuples of members of a universe is fully determined once the universe itself is given, then the truth-values of sentences involving second-order quantifiers are determined in a structure like the ones used for first-order logic. However, if the notion of the set of all sets of n-tuples of members of a universe is specified in terms of some theory about sets or relations, then the universe of a structure must be supplemented by specifications of the domains of the various higher-order variables. No matter what theory one adopts, there are infinitely many choices for such domains compatible with the theory over any infinite universe. This casts doubt on the apparent clarity of the notion of ‘all n-ary relations on a domain’: since the notion cannot be defined categorically in terms of the domain using any theory whatsoever, how could it be well-determined?

Finitary sketches

1997 ◽  
Vol 62 (3) ◽  
pp. 699-707 ◽  
Author(s):  
J. Adámek ◽  
P. T. Johnstone ◽  
J. A. Makowsky ◽  
J. Rosický
Keyword(s):  
Order Logic ◽  
First Order Logic ◽  
Finite Limit ◽  
First Order ◽  
Measurable Cardinals

AbstractFinitary sketches, i.e., sketches with finite-limit and finite-colimit specifications, are proved to be as strong as geometric sketches, i.e., sketches with finite-limit and arbitrary colimit specifications. Categories sketchable by such sketches are fully characterized in the infinitary first-order logic: they are axiomatizable by σ-coherent theories, i.e., basic theories using finite conjunctions, countable disjunctions, and finite quantifications. The latter result is absolute; the equivalence of geometric and finitary sketches requires (in fact, is equivalent to) the non-existence of measurable cardinals.

On the Restraining Power of Guards

1999 ◽  
Vol 64 (4) ◽  
pp. 1719-1742 ◽  
Author(s):  
Erich Grädel
Keyword(s):  
Order Logic ◽  
First Order Logic ◽  
Finite Model ◽  
Model Property ◽  
Tree Model ◽  
First Order ◽  
Bounded Number ◽  
Decidable Classes ◽  
Guarded Fragment ◽  
Almost All

AbstractGuarded fragments of first-order logic were recently introduced by Andréka, van Benthem and Németi; they consist of relational first-order formulae whose quantifiers are appropriately relativized by atoms. These fragments are interesting because they extend in a natural way many propositional modal logics, because they have useful model-theoretic properties and especially because they are decidable classes that avoid the usual syntactic restrictions (on the arity of relation symbols, the quantifier pattern or the number of variables) of almost all other known decidable fragments of first-order logic.Here, we investigate the computational complexity of these fragments. We prove that the satisfiability problems for the guarded fragment (GF) and the loosely guarded fragment (LGF) of first-order logic are complete for deterministic double exponential time. For the subfragments that have only a bounded number of variables or only relation symbols of bounded arity, satisfiability is Exptime-complete. We further establish a tree model property for both the guarded fragment and the loosely guarded fragment, and give a proof of the finite model property of the guarded fragment.It is also shown that some natural, modest extensions of the guarded fragments are undecidable.

First-order logic based on inclusion and abstraction

1982 ◽  
Vol 47 (4) ◽  
pp. 793-808
Author(s):  
John Bacon
Keyword(s):  
Order Logic ◽  
Boolean Logic ◽  
First Order Logic ◽  
Order Restriction ◽  
First Order ◽  
Unit Classes ◽  
Definition Of ◽  
The Universe ◽  
Primitive Notion ◽  
Universe Of Discourse

Quine has shown that set theory may be based on inclusion and abstraction [1937], [1953]. He quantifies over (or abstracts upon) sets of all kinds, of course, including sets of sets. Here I confine Quine's approach to quantification over (abstraction upon) individuals alone, or at any rate their unit classes. Forsaking quantification over sets undercuts Quine's definition of negation, however. Smullyan sketches a first-order restriction of Quine's approach with no bound class variables for which inclusion and abstraction alone are adequate logical primitives [1957, n. 10]. However, the definition of negation requires more than one element in the universe of discourse. This requirement is met for Smullyan because he is doing arithmetic. Here, on the other hand, I presuppose only that the universe is nonempty. Accordingly, I assume a third primitive notion, the empty class. I will show that this threefold basis suffices both for classical first-order logic and for a version of “free” many-sorted logic. The monadic fragment, which I call Boolean logic with abstraction, is intermediate in strength between Boolean class logic and Lesniewski's Ontology. It affords a novel perspective on descriptions, particularly in their generic use.

scholarly journals A First-Order Logic with Frames

2020 ◽  
pp. 515-543 ◽  
Author(s):  
Adithya Murali ◽  
Lucas Peña ◽  
Christof Löding ◽  
P. Madhusudan
Keyword(s):  
Data Structures ◽  
Order Logic ◽  
Separation Logic ◽  
First Order Logic ◽  
Program Logic ◽  
First Order ◽  
Proof Rules ◽  
Local Specifications ◽  
Recursive Definitions ◽  
The Universe

AbstractWe propose a novel logic, called Frame Logic (FL), that extends first-order logic (with recursive definitions) using a construct $$\textit{Sp}(\cdot )$$ Sp ( · ) that captures the implicit supports of formulas— the precise subset of the universe upon which their meaning depends. Using such supports, we formulate proof rules that facilitate frame reasoning elegantly when the underlying model undergoes change. We show that the logic is expressive by capturing several data-structures and also exhibit a translation from a precise fragment of separation logic to frame logic. Finally, we design a program logic based on frame logic for reasoning with programs that dynamically update heaps that facilitates local specifications and frame reasoning. This program logic consists of both localized proof rules as well as rules that derive the weakest tightest preconditions in FL.

Some contributions to definability theory for languages with generalized quantifiers

1982 ◽  
Vol 47 (3) ◽  
pp. 572-586
Author(s):  
John T. Baldwin ◽  
Douglas E. Miller
Keyword(s):  
Order Theory ◽  
Order Logic ◽  
First Order Logic ◽  
Natural Class ◽  
First Order ◽  
First Order Theory ◽  
First Results ◽  
Countably Compact ◽  
Compact Extension ◽  
Almost All

One of the first results in model theory [12] asserts that a first-order sentence is preserved in extensions if and only if it is equivalent to an existential sentence.In the first section of this paper, we analyze a natural program for extending this result to a class of languages extending first-order logic, notably including L(Q) and L(aa), respectively the languages with the quantifiers “there exist un-countably many” and “for almost all countable subsets”.In the second section we answer a question of Bruce [3] by showing that this program cannot resolve the question for L(Q). We also consider whether the natural class of “generalized Σ-sentences” in L(Q) characterizes the class of sentences preserved in extensions, refuting the relativized version but leaving the unrestricted question open.In the third section we show that the analogous class of L(aa)-sentences preserved in extensions does not include (up to elementary equivalence) all such sentences. This particular candidate class was nominated, rather tentatively, by Bruce [3].In the fourth section we show that under rather general conditions, if L is a countably compact extension of first-order logic and T is an ℵ1-categorical first-order theory, then L is trivial relative to T.

First-Order Logic Reasoning Support for the Semantic Web

2009 ◽  
Vol 19 (12) ◽  
pp. 3091-3099 ◽  
Author(s):  
Gui-Hong XU ◽  
Jian ZHANG
Keyword(s):  
Semantic Web ◽  
Order Logic ◽  
First Order Logic ◽  
First Order ◽  
Logic Reasoning

Boolean-valued structures

2018 ◽  
Author(s):  
Tim Button ◽  
Sean Walsh
Keyword(s):  
Model Theory ◽  
Order Logic ◽  
First Order Logic ◽  
Inference Rules ◽  
Mathematical Concepts ◽  
Semantic Framework ◽  
First Order ◽  
Standard Models ◽  
Boolean Valued Model ◽  
Semantic Values

Chapters 6-12 are driven by questions about the ability to pin down mathematical entities and to articulate mathematical concepts. This chapter is driven by similar questions about the ability to pin down the semantic frameworks of language. It transpires that there are not just non-standard models, but non-standard ways of doing model theory itself. In more detail: whilst we normally outline a two-valued semantics which makes sentences True or False in a model, the inference rules for first-order logic are compatible with a four-valued semantics; or a semantics with countably many values; or what-have-you. The appropriate level of generality here is that of a Boolean-valued model, which we introduce. And the plurality of possible semantic values gives rise to perhaps the ‘deepest’ level of indeterminacy questions: How can humans pin down the semantic framework for their languages? We consider three different ways for inferentialists to respond to this question.

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