No description available.

No description available.

The coneptual distinction between logic and control is an important tenet of logic programing. In practice, however, logic program languages use control strategies which profoundly affect the computational behavior of programs. For example, sequential Prolog's depth-first-left-first control is an unfair strategy under which nontermination can easily arise if programs are ill-structured. Formal analyses of logic programs therefore require an explicit formalisation of the control scheme. To this ends, this research introduces an algebraic proccess semantics of sequential logic programs written in Milner's calculus of Communicating Systems (CCS). the main contribution of this semantics is that the control component of a logic programming language is conciesly modelled. Goals and clauses of logic programs correspond semantically to sequential AND and OR agents respectively, and these agents are suitably defined to reflect the control strategy used to traverse the AND/OR computation tree for the program. The main difference between this and other process semantics which model concurrency is that the processes used here are sequential. The primary control strategy studied is standard Prolog's left-first-depth-first control. CCS is descriptively robust, however, and a variety of other sequential control schemes are modelled, including breadth-first, predicate freezing, and nondeterministic strategies. The CCS semantics for a particular control scheme is typically defined hierarchically. For example, standard Prolog control is initially defined in basic CCS using two control operators which model goal backtracking and clause sequencing. Using these basic definitions, higher-level bisimilarities are derived, ehich are more closely mappable to Prolog program constructs. By using variuos algebraic properties of the control operators, as well as the stream domain and theory of observational equivalence from CCS, a programming calculus approach to logic program analysis is permitted. Some example applications using the semantics include proving program termination, verifying transformations which use cut, and characterising some control issues of partial evaluation. Since progress algebras have already been used to model concurrency, this thesis suggests that they are an ideal means for unifying the operational semantics of the sequential and concurrent paradigms of logic programming.

The logic programming language Prolog has been used extensively in conjunction with relational database systems to exploit the similarity between relations and Prolog ground clauses. However, much of the experience gained in the use of Prolog with relational databases has employed characteristics of the language which are independent of the relational model to build user interfaces and perform query transformation. This thesis describes the use of Prolog for developing semantic and object-oriented database systems. Two systems have been developed, one called P/FDM which is based upon the functional data model, and the other called ADAM which integrates ideas from semantic data modelling with constructs developed for sharing behaviour in object-oriented programming languages. The thesis can be considered to be in three sections. The first reviews resarch into semantic data models and object-oriented programming to identify constructs used by different researchers to structure programs and data. The second presents an overview of the design and implementation of P/FDM and ADAM, using Prolog. The final section focusses in detail upon design and implementation issues tackled with both P/FDM and ADAM, relating to the use of keys with object-oriented databases, rule based query optimisation, support for the persistent storage of objects, and the integration of multiple databases. The use of object-oriented databases is illustrated by a chapter which discusses the storage of protein structure data in relational and object-oriented systems.

A resurgence of interest in ontology emerged in the 1990s from the field of information systems engineering. From beginnings such as the Cyc project to codify commonsense knowledge and the Stanford Knowledge Sharing Laboratory efforts to build a shareable ontology of terms, emerged a multitude of ontologies, academic contributions, conferences and commercial companies. / However, does "applied ontology", as a joint field between information systems engineering and philosophy, actually exist? A field that equally informs both engineering and philosophical ontology has obstacles to overcome. For example, according to Grüber's (1993) ubiquitous definition, engineering ontology is a "specification of a conceptualization", whereas in philosophy an ontology is "a systematic account of Existence" - a significant difference. Furthermore, there are philosophical objections to ontology that may undermine its practical application. In this dissertation, we aim to overcome these obstacles by approaching engineering requirements analysis through a particularist metaphysics. More specifically, we argue that engineering 'requirements analysis' can be approached through the ontological question "what exists when the requirements are satisfied?" This approach to requirements analysis forms the core of a joint engineering and philosophical ontology. / The argument obligates us to demonstrate an example of the ontological approach to requirements analysis. We select 'Competitive Intelligence' (CI) as a commercial practice where engineering requirements lend themselves to ontological analysis. A working definition for CI emerges as being "the integration of piecemeal information to support organisational strategy". The major part of the dissertation is a formal analysis (using logic programs) that demonstrates a modified version of this definition can be coherently expressed and used to show the existence of CI as such. The logic also shows CI, as defined, supervenes on other information systems, and depends mainly on a strategic framework. / As such, for the research at hand, the analysis suffices as foundation of an ontology of CI, demonstrates the use of ontology as a requirements analysis approach, and develops a practice of applied ontology that equally informs engineering and philosophy.

Reproduction de : Thèse de 3e cycle : informatique : Grenoble, INPG : 1989. / Titre provenant de l'écran-titre. Bibliogr. p. 151-181.

No description available.

No description available.

Project report (M.C.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 116-118). Also available via the Internet.

A Malay proverb "jika sesat di hujung jalan, baleklah kepangkal jalan" roughly means "if you get lost at the end of the road, go back to the beginning". In going back to the beginning of the road, we learn our mistakes and hopefully will not repeat the same mistake again. Thus, this work investigates the use of formal logic as a practical tool for reasoning why we could not infer or deduce a correct answer from a question posed to a database. An extension of the Prolog interpreter is written to mechanise a theorem-proving system based on Horn clauses. This extension procedure will form the basis of the question-answering system. Both input into and output from this system is in the form of predicate calculus. This system can answer all four classes of questions as classified by Chang and Lee (1973).