Abstract not found

Abstract not found

Minimal Herbrand models for clausal theories are useful in several areas of computer science, e.g. automated theorem proving, program verification, logic programming, databases, and artificial intelligence. In most cases, the conventional model generation algorithms are inappropriate because they generate nonminimal Herbrand models and can be inefficient. This article describes a novel approach for generating the minimal Herbrand models of sets of clauses. The approach builds upon positive unit hyper-resolution (PUHR) tableaux, that are in general smaller than conventional tableaux. PUHR tableaux formalize the approach initially introduced with the theorem prover SATCHMO. Two minimal model generation procedures are described. The first one expands PUHR tableaux depth-first relying on a complement splitting expansion rule and on a form of backtracking involving constraints. A Prolog implementation, named MM-SATCHMO, of this procedure is described. The second minimal model generation pr...

Acknowledgements I wish to thank: 1. my advisor, Bharat Jayaraman, to whom this dissertation owes its existence in an uncountable number of ways, 2. Surya Mantha of Xerox Corporation, for input at various crucial stages, 3. Xerox Corporation, for generously providing funds that supported most of this work, 4. the rest of my committee, namely, Prof. Alan L. Selman and Prof. Kenneth W. Regan, for their interest in my welfare, 5. the secretaries in the department of computer science, for, among other things, shielding me from administrivial vagaries of the University, 6. my friends, for believing in, supporting, and encouraging me through thick andthin. I shall refrain from enumerating names here for fear of making the list longer than the rest of my dissertation.

. Minimal Herbrand models of sets of first-order clauses are useful in several areas of computer science, e.g. automated theorem proving, program verification, logic programming, databases, and artificial intelligence. In most cases, the conventional model generation algorithms are inappropriate because they generate nonminimal Herbrand models and can be inefficient. This article describes an approach for generating the minimal Herbrand models of sets of first-order clauses. The approach builds upon positive unit hyperresolution (PUHR) tableaux, that are in general smaller than conventional tableaux. PUHR tableaux formalize the approach initially introduced with the theorem prover SATCHMO. Two minimal model generation procedures are described. The first one expands PUHR tableaux depth-first relying on a complement splitting expansion rule and on a form of backtracking involving constraints. A Prolog implementation, named MM-SATCHMO, of this procedure is given and its performance on ben...

xi 1 Introduction 1 1.1 Semantic Query Optimization : : : : : : : : : : : : : : : : : : : : : : 3 1.2 High Utility Semantic Knowledge for SQO : : : : : : : : : : : : : : : 6 1.3 Learning Effective and Robust Rules : : : : : : : : : : : : : : : : : : 8 1.4 Closely Related Work : : : : : : : : : : : : : : : : : : : : : : : : : : : 10 1.5 Summary of Contributions : : : : : : : : : : : : : : : : : : : : : : : : 12 1.6 Organization of the Dissertation : : : : : : : : : : : : : : : : : : : : : 13 2 Robustness of Knowledge 15 2.1 Consistency of Rules and Database Changes : : : : : : : : : : : : : : 15 2.2 Definitions of Robustness : : : : : : : : : : : : : : : : : : : : : : : : : 18 2.3 Estimating Robustness : : : : : : : : : : : : : : : : : : : : : : : : : : 19 2.4 Templates for Estimating Robustness : : : : : : : : : : : : : : : : : : 26 2.5 Empirical Demonstration : : : : : : : : : : : : : : : : : : : : : : : : : 27 2.6 Related Uncertainty Measures : : : : : : : : : : : : : : : : : : : ...

Preference Logic Programming (PLP) is an extension of Constraint Logic Programming (CLP) for declaratively specifying optimization problems. In the PLP framework, the definite clauses of a CLP program are augmented by two new kinds of clauses: optimization clauses and arbiter clauses. Optimization clauses specify which predicates are to be optimized and arbiter clauses specify the criteria to be used for optimization. Together, these three kinds of clauses form a preferential theory, for which a possible worlds semantics was first given by Mantha et al. This paper shows how modal concepts can be used to capture the notion of optimization: Essentially, each world in the possibleworlds semantics for a preference logic program is a model of the program, and an ordering over these worlds is enforced by the arbiter clauses in the program. We introduce the notion of preferential consequence as truth in the optimal worlds. We propose an operational semantics that is an extension of SLD deri...

cuses on the formal aspects of language. The layout of the book is pleasant. The examples are numbered in a clear manner. Syntactic and semantic structure listings are all framed in boxes and thus contrasted from the text. Spelling and syntactical errors are few in number. When browsing through the book, one is immediately struck by the amount of structure displays. On 200 pages Ramsay has 75 Frames and 20 Rule structures and countless more auxiliary structures. This results in bothersome reading, since the notation is not comprehensible on first sight. Especially reading Chapter 4 reminded me of reading sparsely annotated C code rather than narrative text. So what is in the book? Chapter 1 is an easy-to-read introduction to the task at hand: formalizing a fragment of English. It briefly explains the prerequisites of compositionality and computational representation that underlie the work. Some examples illustrate the difficulties of formalizing natural language in an intuitive way.

This is a glossary of concepts relevant for computational semantics. The choice of lemmata is based on the concepts mentioned in the Pitlochry document and on previous FraCaS discussions.