COPYRIGHT NOTICE (as suggested by ACM)
The documents contained in these directories are included by contributing authors as a means to ensure timely dissemination of scholarly and technical work on a non-commercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, notwithstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and conditions invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Ineffable inconsistencies
In J.-Y. Béziau and W. Carnielli, editors, Paraconsistency with no Frontiers, volume 4 of Studies in Logic and Practical Reasoning, pp.301-311. Amsterdam: Elsevier Science, 2006. (Preprint available at CLC)
A consistent logic and an inconsistent one can both be based on exactly the same set of formulas and the same single-conclusion consequence relation. This means trouble for the very definition of paraconsistency. Here is how you do the trick, and the way out of it.
Referred at: Citeseer; CSB.

Defining and using deduction systems with Isabelle
(with F. M. Dionísio and P. Gouveia)
In L. Magnani and R. Dossena, editors, Computing, Philosophy and Cognition, pp.271-293. London: College Publications, 2005.
(Preprint available at CLC)
A crash course on implementing and experimenting with diverse deductive systems on Isabelle, a well-known generic theorem proving environment.
Referred at: CSB.

Nearly every normal modal logic is paranormal
Logique et Analyse, 48(189/192):279-300, 2005.
Modal logic could be thought of as a theory of oppositions and negation operators. Instead of boxes and diamonds, one could base it on negations and related operators. Learn here how to do it.
Abstracted or reviewed in: MR2193566; Zbl 1084.03015.
Referred at: CSB.
(Preprint available at CLC)

Modality and paraconsistency
In: Marta Bilkova and Libor Behounek, editors, The Logica Yearbook 2004, Proceedings of the XVIII International Symposium promoted by the Institute of Philosophy of the Academy of Sciences of the Czech Republic, June 2005, pp.213-222. Prague: Filosofia, 2005.
Paraconsistent logics can have usual modal semantics, and in fact any non-degenerate modal logic can be recast as a paraconsistent logic. On the other hand, some paraconsistent logics that are commonly assumed to have a modal character, such as Jaskowski's D2, is not a modal logic at all, according to the contemporary usual meaning of the term.
Referred at: CSB.
(Preprint available at CLC)

On a problem of da Costa
In: Giandomenico Sica, editor, Essays on the Foundations of Mathematics and Logic, v.2, pp.53-69. Monza: Polimetrica, 2005.
On the search of maximal paraconsistent fragments of classical logic.
Referred at: CSB.
(Reprint available at CLE e-prints)

Logics of essence and accident
Bulletin of the Section of Logic, 34(1):43-56, 2005.
An accidental truth is one that is the case, but could have been otherwise. Its opposite notion, that of an essential truth, characterizes propositions that can only be true by way of necessity. This note is a purely modal investigation on the metaphysics of essence and accident.
Abstracted or reviewed in: MR2186213.
Referred at: Citeseer; CSB.
(Preprint available at CLC)

On negation: Pure local rules
Journal of Applied Logic, 3(1):185-219, 2005.
This is a comprehensive and systematic study of negation on a multiple-conclusion environment. Interrelations between many well-known positive properties for abstract deductive systems and for negation symbols are investigated, and negative characterizations of minimally decent classes of logics and logical connectives are favored. Many important proposals of definitions found in the literature are surveyed, and some of them are shown to be severely defective.
Abstracted or reviewed in: MR2126459; Zbl 1063.03013.
Referred at: Citeseer; DBLP; CSB.
(Preprint available at CLE e-prints, CLC)

A logical framework for integrating inconsistent information in multiple databases
(with W. A. Carnielli and S. de Amo)
In: Thomas Eiter and Klaus-Dieter Schewe, editors, Proceedings of the II International Symposium on Foundations of Information and Knowledge Systems (FoIKS 2002), held in Schloß Salzau, Germany, February 2002, pp.67-84.  Lecture Notes in Computer Science 2284, Springer-Verlag, Berlin, 2002.
This is what you should do when finding inconsistency in databases. Based on this study, the paper is a natural continuation and an application of the work started here and further developed here.
Abstracted or reviewed in: Zbl 1044.68049.
Referred at: Citeseer; DBLP; ISI; CSB; ACM Guide.
(Preprint available at CLE e-prints, RUG)

Two's company: "The humbug of many logical values"
(with C. Caleiro, W. A. Carnielli, and M. E. Coniglio)
In: J.-Y. Béziau, editor, Logica Universalis, pp.169-189.  Birkhäuser Verlag, 2005.
The paper builds on the trade-off between bivalence and truth-functionality. A first general algorithm for providing 2-valued ('dyadic') semantics for sufficiently expressive finite-valued logics is proposed. Decidability is not lost, as 2-signed tableaux can be immediately provided for such logics.
Abstracted or reviewed in: MR2134736; Zbl 1076.03006.
Referred at: CSB.
(Preprint available at CLC)

A taxonomy of C-systems
(with W. A. Carnielli)
In: W. A. Carnielli, M. E. Coniglio, and I. M. L. D’Ottaviano, editors, Paraconsistency: The logical way to the inconsistent.  Proceedings of the II World Congress on Paraconsistency (WCP’2000), pp.1-94.  Marcel Dekker, 2002.
A thorough investigation of the foundations of paraconsistent logics.  Relations between logical principles are formally studied, a novel notion of consistency is introduced, the logics of formal inconsistency, and the subclasses of C-systems and dC-systems are defined and studied.  An enormous variety of paraconsistent logics in the literature is shown to constitute C-systems.
Abstracted or reviewed in: MR2008227; Zbl 1036.03022; BSL/ASL.
Referred at: CSB.
(Preprint available at Los Alamos, CLE e-prints, The Mathematics Preprint Server, RUG)

Formal inconsistency and evolutionary databases
(with W. A. Carnielli and S. de Amo)
Logic and Logical Philosophy, 8:115–152, 2000.
The search of logics apt to deal with inconsistent evolving databases is undertaken.  The three-valued maximal paraconsistent logics LFI1 and LFI2 are studied in detail, both at the propositional and at the first-order levels.  Several motivations and examples are given.
(Disgracefully, the journal introduced MANY typos in the printed version. I recommend you thus to stay with the e-version.)
Abstracted or reviewed in: MR1977644; Zbl 1005.03509.
Referred at: Citeseer; CSB.
(Preprint available at CLE e-prints)

Limits for paraconsistent calculi
(with W. A. Carnielli)
Notre Dame Journal of Formal Logic, 40(3):375–390, 1999.
We show how possible-translations semantics can be used to define a logic that is the deductive limit of a sequence of increasingly weaker other logics.  The method is applied in order to define and provide a decision procedure to the deductive limit of the hierarchy of paraconsistent calculi C_n, 0<n<w, introduced by Newton da Costa in the sixties, solving a long standing open problem from the literature.
Abstracted or reviewed in: MR1845624; Zbl 1007.03028.
Referred at: Citeseer; DBLP; CSB.
(Available on-line at Project Euclid)