Deductive databases result from the integration of relational database and logic programming techniques. However, significant problems remain inherent in this simple synthesis from the language point of view. In this paper, we discuss these problems from four different aspects: complex values, object orientation, higherorderness, and updates. In each case, we examine four typical languages that address the corresponding issues.

In this paper, we present an alternative approach to multiple inheritance for typed feature structures. In our approach, a feature structure can be associated with several types coming from different hierarchies (dimensions). In case of multiple inheritance, a type has supertypes from different hierarchies. We contrast this approach with approaches based on a single type hierarchy where a feature structure has only one unique most general type, and multiple inheritance involves computation of greatest lower bounds in the hierarchy. The proposed approach supports current linguistic analyses in constraint-based formalisms like HPSG, inheritance in the lexicon, and knowledge representation for NLP systems. Finally, we show that multi-dimensional inheritance hierarchies can be compiled into a Prolog term representation, which allows to compute the conjunction of two types efficiently by Prolog term unification. 1

LIFE is an experimental programming language proposing to integrate logic programming, functional programming, and object-oriented programming. It replaces first-order terms with ψ-terms, data structures which allow computing with partial information. These are approximation structures denoting sets of values. LIFE further enriches the expressiveness of ψ-terms with functional dependency constraints. We must explain the meaning and use of functions in LIFE declaratively as solving partial information constraints. These constraints do not attempt to generate their solutions but behave as demons filtering out anything else.

We show how the mechanisms of an active/deductive object-oriented model are capable of modeling the information available on the World Wide Web, the paradigmatic example of a large, distributed collection of poorly structured, heterogeneous information, consisting of documents connected by hypertext links. We exhibit the basic features of the object model, including the schema definition language, the query language with multiple roles, the basic update operations, and a form of active rules, and a compilation of the mentioned features into a fragment of LDL++, which is essentially Datalog extended with non-determinism and a form of stratified negation. The proposed compilation has a twofold aim. On one side, it should provide an abstract implementation level, where the object model is declaratively reconstructed and its semantics clarified. On the other side, the proposed compilation should form the basis of a realistic implementation, as LDL++ can be efficiently executed, and suppor...

We discuss the advantages of using a logic system for knowledge representation which is based on descriptions, rather than predicates, and which embodies two fundamental ideas for structuring knowledge that are distilled from semantic networks and frame based languages: inheritance and attributions. Taxonomic reasoning on a lattice of descriptions combined with deduction strategies defined at the metalevel provides the knowlegde base with the capability to deal with complex problem solving tasks. I.

We show how a fragment of the logical data language LDL++ can be used to define an abstract machine supporting the essence of active/deductive object-oriented databases. We exhibit a compilation into the mentioned logic language of the basic features of the object model, including the schema definition language, the query language with multiple roles, the basic update operations, and a form of active rules. The target logic language, which is essentially Datalog extended with non-determinism and a form of stratified negation, has been chosen with a twofold aim. On one side, it should provide an abstract implementation level, where the object model is declaratively reconstructed and its semantics clarified. On the other side, the proposed compilation should form the basis...

Abstract not found