Persistent constraints in constraint handling rules

Hariolf Betz, Frank Raiser, and Thom Frühwirth. Persistent constraints in constraint handling rules. 2010, 23rd Workshop on (Constraint) Logic Programming, Workshop


In the most abstract de nition of its operational semantics, the declarative and concurrent programming language CHR is trivially non-terminating for a signi cant class of programs. Common re finements of this de nition, in closing the gap to real-world implementations, compromise on declarativity and/or concurrency. Building on recent work and the notion of persistent constraints, we introduce an operational semantics avoiding trivial non-termination without compromising on its essential features.