Constraint Logic Programming (CLP) is a merger of two declarative paradigms: constraint solving and logic programming. Although a relatively new field, CLP has progressed in several quite different directions. In particular, the early fundamental concepts have been adapted to better serve in different areas of applications. In this survey of CLP, a primary goal is to give a systematic description of the major trends in terms of common fundamental concepts. The three main parts cover the theory, implementation issues, and programming for applications.

The Constraint Logic Programming Scheme defines a class of languages designed for programming with constraints using a logic programming approach. These languages are soundly based on a unified framework of formal semantics. In particular, as an instance of this scheme with real arithmetic constraints, the CLP(R) language facilitates and encourages a concise and declarative style of programming for problems involving a mix of numeric and non-numeric computation. In this paper we illustrate the practical applicability of CLP(R) with examples of programs to solve electrical engineering problems. This field is particularly rich in problems that are complex and largely numeric, enabling us to demonstrate a number of the unique features of CLP(R). A detailed look at some of the more important programming techniques highlights the ability of CLP(R) to support well-known, powerful techniques from constraint programming. Our thesis is that CLP(R) is an embodiment of these techniques in a langu...

Preference logic programming (PLP) is an extension of constraint logic programming (CLP) for declaratively specifying problems requiring optimization or comparison and selection among alternative solutions to a query. In the PLP framework, the definite clauses of a constraint logic program are augmented by two new kinds of clauses, which we call 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. We illustrate their use with representative examples: one from dynamic programming and another from ambiguity resolution in grammars. We formalize the semantics of PLP using concepts from modal logic: Essentially, each world in the possible-worlds 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 a new notion called preferential consequence to refer to tru...

In constraint logic programming (CLP) systems, the standard technique for dealing with hard constraints is to delay solving them until additional constraints reduce them to a simpler form. For example, the CLP(R) system delays the solving of nonlinear equations until they become linear, when certain variables become ground. In a naive implementation, the overhead of delaying and awakening constraints could render a CLP system impractical. In this paper, a framework is developed for the specification of wakeup degrees which indicate how far a hard constraint is from being awoken. This framework is then used to specify a runtime structure for the delaying and awakening of hard constraints. The primary implementation problem is the timely awakening of delayed constraints in the context of temporal backtracking, which requires changes to internal data structures be reversible. This problem is resolved efficiently in our structure. 1 Introduction The Constraint Logic Programming scheme [7...

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.