This paper presents a parallel execution system (PDP: Prolog
Distributed Processor), for efficiently supporting both
Independent_AND\OR parallelism on distributed memory
multiprocessors. The system is composed of a set of workers
with a hierarchic structure scheduler. Each worker operates
on its own private memory and interprocessor communication
is performed only by the passing of messages. Different
scheduling policies have been studied, and granularity controls
have been introduced for each kind of parallelism. PDP has been
implemented on a transputer network and performance results
show that PDP provides a high speedup for coarse grain parallel
programs.