We propose a novel formalism, called Frame Logic (abbr., F-logic), that accounts in a clean and declarative fashion for most of the structural aspects of object-oriented and frame-based languages. These features include object identity, complex objects, inheritance, polymorphic types, query methods, encapsulation, and others. In a sense, F-logic stands in the same relationship to the objectoriented paradigm as classical predicate calculus stands to relational programming. F-logic has a model-theoretic semantics and a sound and complete resolution-based proof theory. A small number of fundamental concepts that come from object-oriented programming have direct representation in F-logic; other, secondary aspects of this paradigm are easily modeled as well. The paper also discusses semantic issues pertaining to programming with a deductive object-oriented language based on a subset of F-logic.

The Context Interchange strategy presents a novel perspective for mediated data access in which semantic conflicts among heterogeneous systems are not identified a priori, but are detected and reconciled by a context mediator through comparison of contexts axioms corresponding to the systems engaged in data exchange. In this article, we show that queries formulated on shared views, export schema, and shared “ontologies ” can be mediated in the same way using the Context Interchange framework. The proposed framework provides a logic-based object-oriented formalism for representing and reasoning about data semantics in disparate systems, and has been validated in a prototype implementation providing mediated data access to both traditional and web-based information sources. Categories and Subject Descriptors: H.2.4 [Database Management]: Systems—Query processing; H.2.5 [Database Management]: Heterogeneous Databases—Data translation

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This paper presents a novel deductive object-oriented database language, called ROL (Rule-based Object Language), which is being developed at the University of Regina. ROL effectively integrates important features of object-oriented databases and deductive databases into a uniform framework. It supports object identity, complex objects, classes, class hierarchy, multiple inheritance with overriding, and schema. It also supports structured values such as functor objects and sets, treats them as first class citizens, and provides powerful mechanisms for representing both partial and complete information on sets. It is an extension of pure valued-oriented deductive languages such as Datalog and LDL (without grouping) and subsumes them as special cases. Another novelty is the introduction of a new ordering which can capture the intended semantics of nested sets. The ROL language is given a logical semantics based on this new ordering that accounts in a clean and declarative fashi...

. We present declarative and procedural semantics for a deductive object-oriented language, Gulog. The declarative semantics is based on preferred minimal models. We describe both bottom-up and top-down query evaluation procedures and show that they are sound with respect to the declarative semantics. The results contribute to our understanding of the interaction of inheritance, overriding and deduction in the presence of both functional and set-valued methods, and multiple inheritance. Keywords: complex objects, deductive databases, fixpoint semantics, procedural semantics, knowledge bases, object-oriented databases, rule based 1. Introduction The aim of this paper is to propose a simple mathematical foundation for objectoriented systems with deduction. In particular, we present a declarative and procedural semantics for a simple language that includes classes, objects, functional and set-valued methods, (multiple) inheritance, overriding, and derived methods and predicates with the...

The Context Interchange strategy [5; 12] presents a novel solution to mediated data access in which semantic conflicts among heterogeneous systems are automatically detected and reconciled by a Context Mediator using the contexts associated with the systems involved. We have implemented these mediation services using the ECLiPSe 1 platform and have deployed them in several applications giving access to on-line database and web services.

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This paper discusses the algorithm we are using for the mediation of queries to disparate information sources in a Context Interchange system, where information sources may have di erent interpretations arising from their respective context. Queries are assumed to be formulated without regard for semantic heterogeneity, and are rewritten to corresponding mediated queries by taking into account the semantics of data codi ed in axioms associated with sources and receivers (the corresponding context theories). Our approach draws upon recent advances in abductive logic programming and presents an integration of techniques for query rewriting and semantic query optimization. We also demonstrate how thiscanbe e ciently implemented using the constraint logic programming system ECLiPSe. 1

This paper proposes a new approach to model deductive object databases. Each object database is described by means of a Datalog language extended with extensional updates, called U-Datalog. Objects can change state and cooperate. We introduce an extension of U-Datalog to approach the problem of composition among object databases. It can be used for modular database design and for cooperation among deductive objects. The resulting language has a clear semantics for the evolution of objects and for modeling the transactional behavior of the resulting database. Finally, we describe some architectural issues of the prototype which has been developed.

We present a typed polymorphic calculus that supports a general mechanism for view definition and object sharing among classes. In this calculus, a class can contain inclusion specifications of objects from other classes. Each such specification consists of a em predicate determining the subset of objects to be included and a viewing function under which those included objects are manipulated. Both predicates and viewing functions can be any type consistent programs definable in the polymorphic calculus. Inclusion specifications among classes can be cyclic, allowing mutually recursive class definitions. These features achieve flexible view definitions and wide range of class organizations in a compact and elegant way. Moreover, the calculus provides a suitable set of operations for views and classes so that the programmer can manipulate views and classes just the same way as one deals with ordinary records and sets. The proposed calculus uniformly integrates views and classes in a polymorphic type system of a database programming language similar to Machiavelli. The calculus has a type inference algorithm that relieves the programmer from complicated type declarations of views and classes. The polymorphic type system of the calculus is also shown to be sound, which guarantees complete static check of type consistency of programs involving classes and views. Through these properties, the programmer can enjoy full advantages of polymorphism and type inference when writing object-oriented database programs.