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

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

info:eu-repo/semantics/publishedVersio

A Mathematical Treatment of Defeasible Reasoning and its Implementation

We present a mathematical approach to defeasible reasoning. This approach is based on the notion of specificity introduced by Poole and the theory of warrant presented by Pollock. We combine the ideas of the two. This main contribution of this paper is a precise well-defined system which exhibits correct behavior when applied to the benchmark examples in the literature. We prove that an order relation can be introduced among equivalence classes under the equi-specificity relation. We also prove a theorem that ensures the termination of the process of finding the justified facts. Two more lemmas define a reduced search space for checking specificity. In order to implement the theoretical ideas, the language is restricted to Horn clauses for the evidential context. The language used to represent defeasible rules has been restricted in a similar way. The authors intend this work to unify the various existing approaches to argument-based defeasible reasoning

An Alternative Semantics for Argumentative Systems

Defeasible argumentation is one of the approaches that addresses the challenges arising when we reason defeasibly, with several formalisms in the literature reaching a mature state. Considering that most of these theories eventually shifted their semantics towards dialectical characterizations, we believe that a sufficiently generic model of the process of reasoning in dialectical terms could also serve as an abstract model of what happens inside an argumentative system. To that end, we develop in this article a formal model of dialectical reasoning and explore its role as an alternative semantics for argumentation theories

Towards a Generalized Database System with Multiple Interfaces

We have applied logic programming to the problem of designing knowledge representation systems. This report describes a Generalized Database System, PRODB, that has been implemented in Prolog. It also describes two extensions to the basic PRODB core. First, knowledge representation and consistency-checking features have been added to PRODB to enhance its ability to consistently represent knowledge, especially in an Engineering domain. Second, extensions to Prolog\u27s definite clause grammar mechanism have been used to create interfaces to a knowledge base directly from grammars describing the input languages. The interface to the system is derived directly from the grammars, so this part of the system is easy to tailor. In addition, we are able to use different grammars at different times in order to have multiple interfaces to the same knowledge base system

On the construction of Dialectical Databases

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 argumentationdriven 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

A general approach to the implementation of action theories

Much effort has been dedicated to provide a general model of agents working in complex environments. This research focuses on the high level cognition used in determining the behavior of the agent. The language of the Situation Calculus represents a very useful way of modeling an agent’s knowledge of its environment. One of its advantages is that there exist methods to derive an executable program from a basic set of axioms. This program can then be used to determine the actions that are necessary in order to accomplish certain goal states. The main objective of this line of work is to obtain an automatic way of deriving such an executable program.Eje: Inteligencia artificialRed de Universidades con Carreras en Informática (RedUNCI