An execution scheme for interactive problem-solving in concurrent constraint logic programming languages

13 years 4 months ago

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Van Emden's incremental queries address the inadequacy of current Prolog-style querying mechanism in most logic programming systems for interactive problem-solving. In the context of constraint logic programming, incremental queries involve adding new constraints or deleting old ones from a query after a solution is found. This paper presents an implementation scheme IQ of incremental queries in Constraint Pandora, which defines a class of non-deterministic concurrent constraint logic programming languages. We use Van Hentenryck and Le Provost's scheme (VHLP-scheme hereafter), a re-execution approach, as a starting point. Re-execution is costly in concurrent languages, in which process creation and inter-process communications are common operations. The main idea of IQ is that the basic trail unwinding operation used in backtracking is more efficient than re-execution in reaching an execution context along a recorded execution path. We modify the conventional trail-unwinding...

Jimmy Ho-Man Lee, Ho-fung Leung

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