Strong Joinability Analysis for Graph Transformation Systems in CHR

The notion of confluence is prevalent in graph transformation systems (GTS) as well as constraint handling rules (CHR). This work presents a generalized embedding of GTS in CHR that allows to consider strong derivations in confluence analyses. Confluence of a terminating CHR program is decidable, whereas confluence of a terminating GTS is undecidable. We show that observable confluence in CHR coincides with a sufficient criterion for confluence of the embedded GTS. For this purpose the automatic confluence check for CHR can be reused.