P-Prolog is put forward as an alternative proposal to the difficulties faced in the main research areas of parallel logic programmings, which have been studied. P-Prolog provides the advantages of guarded Horn clauses while retaining don't know non-determinism where required. This monograph presents also an or-tree model and an implementation scheme for it, to combine and- and or- parallelism with reasonable efficiency. The model and implementation scheme discussed can be applied to P-Prolog and other parallel logic languages. Contents: Theory of Logic ProgrammingA Survey of Parallel Logic LanguagesP-Prolog: A Parallel Logic Programming Language — Basic Concepts of P-Prolog, Syntax and Semantics, Programming Example and Comparison with Other Languages, Programming in P-Prolog, Re-examination of P-Prolog in Terms of TheoryBinary Tree ExpressionEfficient Memory Management for Multiple EnvironmentsCombining And-parallelism and Or-parallelismConclusion Readership: Computer scientists. Keywords:Logic Programming;Parallel;Concurrency;Computer Language;Prolog Implementation;Declarative Programming;Search Trees;AI;Symbolic Processing