Constraint Handling Rules (CHRs) are a powerful rule based language for specifying constraint solvers. Critical for any rule based language is the notion of confluence, and for terminating CHRs there is a decidable test for confluence. But many CHR programs that in practice are confluent fail this confluence test. The problem is that the states that illustrate non-confluence are not reachable i...

several studies suggest that invertebrate abundance and richness are disrupted and reset at confluences. thus, junctions contribute disproportionately to the overall aquatic biodiversity of the river. in general terms, authors have reported high abundance and diversity due to the major physical heterogeneity at junctions. however, data are still scarce and uncertainties are plentiful.the impact...

We consider cut-elimination in the sequent calculus for classical first-order logic. It is well known that this system, in its most general form, is neither confluent nor strongly normalizing. In this work we take a coarser (and mathematically more realistic) look at cut-free proofs. We analyze which witnesses they choose for which quantifiers, or in other words: we only consider the Herbrand-d...

We investigate con uence properties for concurrent systems of message-passing processes, because such properties have proved to be useful for a variety of applications, ranging from reasoning about concurrent objects to mobile and high-speed telecommunication protocols. Roughly, con uence means that for every two computations starting from a common system state, it is possible to continue the c...

This paper describes the Conditional Confluence tool, a fully automatic confluence checker for first-order conditional term rewrite systems. The tool implements various confluence criteria that have been proposed in the literature. A simple technique is presented to test conditional critical pairs for infeasibility, which makes conditional confluence criteria more useful. Detailed experimental ...

We study the combination of the following already known ideas for showing confluence of unconditional or conditional term rewriting systems into practically more useful confluence criteria for conditional systems: Our syntactic separation into constructor and non-constructor symbols, Huet’s introduction and Toyama’s generalization of parallel closedness for non-terminating unconditional systems...

Combining term rewriting and modal logics, this paper addresses confluence and termination of rewrite systems introduced for only-knowing logics. The rewrite systems contain a rule scheme that gives rise to an infinite number of critical pairs, hence we cannot check the joinability of every critical pair directly, in order to establish local confluence. We investigate conditions that are suffic...

Confluence is an important property for any kind of rewrite system including CHR, which is a general-purpose declarative committedchoice language consisting of multi-headed guarded rules. CHR can yield a confluence problem, because of non-determinism in the choice of rules using the abstract semantics. Confluence in CHR is an ongoing research topic, because it provides numerous benefits for imp...

Previous results on confluence for Constraint Handling Rules, CHR, are generalized to take into account user-defined state equivalence relations. This allows a much larger class of programs to enjoy the advantages of confluence, which include various optimization techniques and simplified correctness proofs. A new operational semantics for CHR is introduced that reduces notational overhead sign...