Detecting Unsolvable Queries for de nite Logic Programs

Detecting Unsolvable Queries for Definite Logic Programs

In solving a query, the SLD proof procedure for definite programs sometimes searches an infinite space for a non existing solution. For example, querying a planner for an unreachable goal state. Such programs motivate the development of methods to prove the absence of a solution. Considering the definite program and the query ← Q as clauses of a first order theory, one can apply model generator...

Declarative Diagnosis of Constraint Programs an assertion based approach

This paper discusses adaptation of the declarative diagnosis techniques for the use in constraint logic programming The objective is to show how the well known concepts are to be modi ed in this setting In particular the paper outlines basic algorithms for diagnosing incorrectness errors and insu ciency errors for constraint programs over arbitrary domains The main focus is on de ning kinds of ...

Complexity of Query Answering in LogicDatabases with Complex

This paper characterizes the computational complexity of nonrecursive queries in logic databases with complex values. Queries are represented by Horn clause logic programs. Complex values are represented by terms in equational theories ( nite sets and multisets are examples of such complex values). We show that the problem of whether a query has a nonempty answer is NEXP-hard for nonrecursive r...

Proving Failure of Queries for De nite Logi Programs

Max-planck-institut F Ur Informatik Complexity of Nonrecursive Logic Programs with Complex Values K I N F O R M a T I K We Thank

We investigate complexity of the SUCCESS problem for logic query languages with complex values: check whether a query de nes a nonempty set. The SUCCESS problem for recursive query languages with complex values is undecidable, so we study the complexity of nonrecursive queries. By complex values we understand values such as trees, nite sets, and multisets. Due to the well-known correspondence b...