Some methodological issues in the design of CIAO, a generic, parallel concurrent constraint logic programming system

We informally discuss several issues related to the parallel execution of logic programming systems and concurrent logic programming systems, and their generalization to constraint programming. We propose a new view of these systems, based on a particular definition of parallelism. We argue that, under this view, a large number of the actual systems and models can be explained through the application, at different levels of granularity, of only a few basic principles: determinism, non-failure, independence (also referred to as stability), granularity, etc. Also, and based on the convergence of concepts that this view brings, we sketch a model for the implementation of several parallel constraint logic programming source languages and models based on a common, generic abstract machine and an intermediate kernel language.