A Framework for Combining Defeasible Argumentation with Labeled Deduction

In the last years, there has been an increasing demand of a variety of logical systems, prompted mostly by applications of logic in AI and other related areas. Labeled Deductive Systems (LDS) were developed as a flexible methodology to formalize such a kind of complex logical systems. Defeasible argumentation has proven to be a successful approach to formalizing commonsense reasoning, encompassing many other alternative formalisms for defeasible reasoning. Argument-based frameworks share some common notions (such as the concept of argument, defeater, etc.) along with a number of particular features which make it difficult to compare them with each other from a logical viewpoint. This paper introduces LDSar, a LDS for defeasible argumentation in which many important issues concerning defeasible argumentation are captured within a unified logical framework. We also discuss some logical properties and extensions that emerge from the proposed framework.Comment: 15 pages, presented at CMSRA Workshop 2003. Buenos Aires, Argentin

Defeasible Logic Programming: An Argumentative Approach

The work reported here introduces Defeasible Logic Programming (DeLP), a formalism that combines results of Logic Programming and Defeasible Argumentation. DeLP provides the possibility of representing information in the form of weak rules in a declarative manner, and a defeasible argumentation inference mechanism for warranting the entailed conclusions. In DeLP an argumentation formalism will be used for deciding between contradictory goals. Queries will be supported by arguments that could be defeated by other arguments. A query q will succeed when there is an argument A for q that is warranted, ie, the argument A that supports q is found undefeated by a warrant procedure that implements a dialectical analysis. The defeasible argumentation basis of DeLP allows to build applications that deal with incomplete and contradictory information in dynamic domains. Thus, the resulting approach is suitable for representing agent's knowledge and for providing an argumentation based reasoning mechanism to agents.Comment: 43 pages, to appear in the journal "Theory and Practice of Logic Programming

PRODB: An Experimental Generalized Database System User\u27s Manual

The following notes document in a succinct manner the use of the system PRODB. The system is still evolving and several new features are in the process of being added. PRODB is a prototype system that is being used as an exploration vehicle of the possible extensions to the relational model through logic programming. The system consists of a relational database system having a relational algebra type language as a query language. It is written in Prolog and it extends the capabilities of Prolog predicates with the relational algebra operators for handling the database structure. The database system currently provides the set theoretic operations (union, intersection, difference and product), join, project and select. The relations can be defined over any domain that can be defined using a Prolog predicate. Primary keys for the relations should be defined and their uniqueness is maintained. Facilities exist for defining assertions over the contents of the relations. Those assertions are predicates that constrain the set of legal tuples that can be part of a relation. The consistency of the database is checked and maintained with respect to the set of assertions and domains. Actions are daemons associated with the update operations and can be defined by the user as Prolog predicates that will be triggered by those operations. Actions can involve any Prolog (or PRODB) predicate and allow the definition of side effect behavior when an update operation is performed. A transaction can be started and all the operations executed inside of it can be started and all the operations executed inside of it can be rolled-back to the point when the transaction was started. Time is associated with the creation of the relations and with the insertion of tuples in the form of a time-stamp. That time-stamp is shown in the printouts of schemas and, by using the appropriate predicate, also in the printouts of relations. A predicate for selecting tuples according with their time of insertion is defined. There are several predefined comparison operators and predicates. The usual aggregate predicates are available including some handling time. A built-in help facility is available (see the Miscellaneous paragraph) and appropriate error messages are issues whenever an error condition is reached. The system is capable of handling several databases at the same time and all the relational operations can take arguments from different databases. Also the referential integrity can be enforced across databases. Different scenarios can be developed in that way and, in conjunction with the transaction facility, the seed for an exploration capability is in place. First the operation handling complete databases as objects are presented. Then, the relative level operations for handling tuples and the syntax of the implemented relational algebra operations for handing tuples and the syntax of the implemented relational algebra operators is introduced. After that, there is a brief discussion over how to define assertions and actions for the database. Finally the time related predicates, transaction facility and some miscellaneous predicates are described

A Justification Finder

The technical report presents a succinct description of the Justification Finder (if). The system if is a practical implementation of the theoretical ideas introduced elsewhere (see the technical report On the Logic of Defeasible Reasoning , G Simari, WUCS-89-12). It is used to explore and validate those ideas. The system provides support for defeasible reasoning in a Prolog environment. The complete Prolog language is available and only a few new predicates are introduced extending the reserved words of the language. We will present the theoretical underpinnings of the system in a very terse manner. The reader is referred to [1] for a more complete account of defeasible reasoning

Building precompiled knowledge in ODeLP

Argumentation systems have substantially evolved in the past few years, resulting in adequate tools to model some forms of common sense reasoning. This has sprung a new set of argument-based applications in diverse areas. In previous work, we defined how to use precompiled knowledge to obtain significant speed-ups in the inference process of an argument-based system. This development is based on a logic programming system with an argumentation-driven inference engine, called Observation Based Defeasible Logic Programming (ODeLP). In this setting was first presented the concept of dialectical databases, that is, data structures for storing precompiled knowledge. These structures provide precompiled information about inferences and can be used to speed up the inference process, as TMS do in general problem solvers. In this work, we present detailed algorithms for the creation of dialectical databases in ODeLP and analyze these algorithms in terms of their computational complexity.Red de Universidades con Carreras en Informática (RedUNCI

An argumentation framework with uncertainty management designed for dynamic environments

Nowadays, data intensive applications are in constant demand and there is need of computing environments with better intelligent capabilities than those present in today's Database Management Systems (DBMS). To build such systems we need formalisms that can perform complicate inferences, obtain the appropriate conclusions, and explain the results. Research in argumentation could provide results in this direction, providing means to build interactive systems able to reason with large databases and/or di erent data sources. In this paper we propose an argumentation system able to deal with explicit uncertainty, a vital capability in modern applications. We have also provided the system with the ability to seamlessly incorporate uncertain and/or contradictory information into its knowledge base, using a modular upgrading and revision procedurePresentado en el X Workshop Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

On the connection between default logic and DELP

In this paper, we establish a relation between an argumentation based system: Defeasible Logic Programming (DELP), and a nonmonotonic system: Reiter’s Default Logic. This relation is achieved by introducing a variant of DELP and a transformation that maps default theories to defeasible logic programs. The transformation allows to associate the answers of a DELP Interpreter with the consequences, credulous and skeptical, of the default theory. Thus, this work establishes a link between a well understood nonmonotonic system and a argumentation based system. This link could be studied separately and could be exploited for the development of the latter system.Red de Universidades con Carreras en Informática (RedUNCI

Introduction to the special issue on belief revision, argumentation, ontologies, and norms

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