Timed Soft Concurrent Constraint Programs: An Interleaved and a Parallel Approach
This work provides a theoretical framework for coordinating agents in logic programming, but it is incremental as it builds on existing Concurrent Constraint Programming with timed and soft extensions.
The authors introduced a timed and soft extension of Concurrent Constraint Programming, incorporating bounded asynchrony and soft constraints with preference thresholds to coordinate agents based on time and preference values.
We propose a timed and soft extension of Concurrent Constraint Programming. The time extension is based on the hypothesis of bounded asynchrony: the computation takes a bounded period of time and is measured by a discrete global clock. Action prefixing is then considered as the syntactic marker which distinguishes a time instant from the next one. Supported by soft constraints instead of crisp ones, tell and ask agents are now equipped with a preference (or consistency) threshold which is used to determine their success or suspension. In the paper we provide a language to describe the agents behavior, together with its operational and denotational semantics, for which we also prove the compositionality and correctness properties. After presenting a semantics using maximal parallelism of actions, we also describe a version for their interleaving on a single processor (with maximal parallelism for time elapsing). Coordinating agents that need to take decisions both on preference values and time events may benefit from this language. To appear in Theory and Practice of Logic Programming (TPLP).