
Authors:
Newton C.A.da COSTA, F.A.DORIA and Marcelo TSUJI
Title:The undecidability of formal definitions in the theory of finite groups
Pages:5663
File:bibtex
Abstract ( + )
[In this paper a set of explicit expressions for a family of finite groups will be constructed in the language of ZermeloFraenkel plus the Axiom of Choice set theory in such a way that there is no general procedure to decide whether a given expression of this set is representing a finite solvable group or not.

Authors:
Marcelo F.FRIAS, Gabriel A.BAUM, Armando M.HAEBERER and Paulo A.S.VELOSO
Title:Fork algebras are representable
Pages:6475
File:bibtex
Abstract ( + )
Fork algebras are extensions of relation algebras by a new binary operator, fork. This extension is motivated by programming needs, as a tool for reasoning about program behavior. Their expressiveness was already established: in any proper fork algebra (a standard model) every binary relation that is firstorder definable is also denoted by a fork term. This shows that the expressive power of proper fork algebras encompasses that of firstorder logic with equality. Here we complement this result by a representation theorem: every atomic abstract fork algebra is isomorphic to a proper one.

Authors:
Robert K.MEYER
Title:Rationalizing relevant primitives, of course!
Pages:7679
File:bibtex
Abstract ( + )
Alonzo Church introduced propositional quantifiers as "original equipment" into theories of relevant implication. He was followed in this by Anderson, Belnap, and Dunn. In some of my own researches into defining some primitives in terms of others are reported. The following is a partial list for three systems.

Authors:
Ewa GRACZYNSKA
Title:On some operators on pseudovarieties II
Pages:8088
File:bibtex
Abstract ( + )
This is a continuation of my paper On some operators on pseudovarieties. We adopt the HSP Theorem of G. Birkhoff and the Theorem of H. Lakser, R. Padmanabhan, C.R. Platt, for pseudovarieties. Some of the results were presented at the 48 Workshop on General Algebra, in Linz (Austria), 25 June, 1994.

Authors:
Jozef WAJSZCZYK
Title:The logic of dichotomic changes
Pages:8997
File:bibtex
Abstract ( + )
This paper is intended to present the propositional calculus MLC called the Minimal Logic of Change or the Logic of Dichotomic Changes. The calculus covers only the cases of dichotomic, step changes.

Authors:
Valentin GORANKO
Title:A note on derivation rules in modal logic
Pages:98104
File:bibtex
Abstract ( + )
he traditional Hilbertstyle deductive apparatus for Modal logic in abroad sense (incl. temporal, dynamic, epistemic etc. logics) seems to have exhausted the potential of its standard form i.e. with only rules of inference being Modus Ponens, Necessitation and Substitution, plusQuantifier rules for the firstorder versions. Various expressively strong and/or goaloriented extended modal languages have been recently introduced which cannot be adequately axiomatized within that traditional framework and require specific additional rules ofinference. Besides, introduction of additional rules has proved to be efficient for increasing the expressiveness of the language by means of eliminating unwanted models (those in which the new rules do not preserve validity) and thus depicting more precisely the intended semantics.

Authors:
Takao INOUE
Title:Hintikka formulas as axioms of refutation calculus, a case study
Pages:105114
File:bibtex
Abstract ( + )
In this paper, we shall propose an elegant Hilbertstyle axiomatic rejection (that is, refutation calculus) HL_{1} for Ishimoto's propositional fragment L_{1} of Lesniewski's ontology L with Hintikka formulas as axioms.

Authors:
Takao INOUE
Title:The single axiomschema of March 8th
Pages:115115
File:bibtex
Abstract ( + )
[Abstract]