0 Introduction

The rapid growth of distributed processing has led to a need for a coordinating framework for the standardization of Open Distributed Processing (ODP). This Reference Model provides such a framework. It creates an architecture within which support of distribution, interworking and portability can be integrated.

The Reference Model of Open Distributed Processing, ITU-T Recommendations X.901 to X.904 | ISO/IEC 10746, is based on precise concepts derived from current distributed processing developments and, as far as possible, on the use of formal description techniques for specification of the architecture.

The Reference Model consists of

-- ITU-T Rec. X.901 | ISO/IEC 10746-1: Overview: contains a motivational overview of ODP giving scoping, justification and explanation of key concepts, and an outline of the ODP architecture. It contains explanatory material on how this Reference Model is to be interpreted and applied by its users, who may include standards writers and architects of ODP systems. It also contains a categorization of required areas of standardization expressed in terms of the reference points for conformance identified in ITU-T Recommendation X.903 | ISO/IEC 10746-3. This part is not normative.

-- ITU-T Rec. X.902 | ISO/IEC 10746-2: Foundations: contains the definition of the concepts and analytical framework for normalised description of (arbitrary) distributed processing systems. It introduces the principles of conformance to ODP standards and the way in which they are applied. This is only to a level of detail sufficient to support ITU-T Recommendation X.903 | ISO 10746-3 and to establish requirements for new specification techniques. This part is normative.

-- ITU-T Rec. X.903 | ISO/IEC 10746-3: Architecture: contains the specification of the required characteristics that qualify distributed processing as open. These are the constraints to which ODP standards must conform. It uses the descriptive techniques from ITU-T Recommendation X.902 | ISO/IEC 10746-2. This part is normative.

-- ITU-T Rec. X.904 | ISO/IEC 10746-4: Architectural semantics: contains a formalization of the ODP modelling concepts defined in ITU-T Recommendation X.902 | ISO/IEC 10746-2 clauses 8 and 9. The formalization is achieved by interpreting each concept in terms of the constructs of the different standardized formal description techniques. This part is normative.

This Recommendation | part of ISO/IEC 10746 contains one annex (this annex forms an integral part of the Reference Model).