The rapid growth of distributed processing has lead to a need for a coordinating framework for the standardization of
Open Distributed Processing (ODP). This Reference Model of ODP provides such a framework. It creates an
architecture within which support of distribution, interworking, interoperability and portability can be integrated.
The Basic Reference Model of Open Distributed Processing (RM-ODP), (see ITU-T Recs. 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 RM-ODP consists of:
? ITU-T Rec. X.901 | ISO/IEC 10746-1: 2YHUYLHZ:_ Contains a motivational overview of ODP giving
scooping, justification and explanation of key concepts, and an outline of ODP architecture. This part is
? ITU-T Rec. X.902 | ISO/IEC 10746-2: )RXQGDWLRQV:_ Contains the definition of the concepts and
analytical framework and notation for normalized description of (arbitrary) distributed processing
systems. This is only to a level of detail sufficient to support ITU-T Rec. X.903 | ISO/IEC 10746-3 and to
establish requirements for new specification techniques. This part is normative.
? ITU-T Rec. X.903 | ISO/IEC 10746-3: $UFKLWHFWXUH: 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 Rec. X.902 | ISO/IEC 10746-2.
This part is normative.
? ITU-T Rec. X.904 | ISO/IEC 10746-4: $UFKLWHFWXUDO_6HPDQWLFV:_Contains a formalisation of the ODP
modeling concepts defined in ITU-T Rec. X.902 | ISO/IEC 10746-2, clauses 8 and 9, and a formalisation
of the viewpoint languages of ITU-T Rec. X.903 | ISO/IEC 10746-3. The formalisation is achieved by
interpreting each concept in terms of the constructs of the different standardized formal description
techniques. This part is normative.
The purpose of this Recommendation | International Standard is to provide an architectural semantics for ODP. This
essentially takes the form of an interpretation of the basic modeling and specification concepts of ITU-T Rec. X.902 |
ISO/IEC 10746-2 and viewpoint languages of ITU-T Rec. X.903 | ISO/IEC 10746-3, using the various features of
different formal specification languages. An architectural semantics is developed in four different formal specification
languages: LOTOS, ESTELLE, SDL and Z. The result is a formalization of ODP's architecture. Through a process of
iterative development and feedback, this has improved the consistency of ITU-T Rec. X.902 | ISO/IEC 10746-2 and
ITU-T Rec. X.903 | ISO/IEC 10746-3.
An architectural semantics provides the additional benefits of:
? assisting the sound and uniform development of formal descriptions of ODP systems; and
? of permitting uniform and consistent comparison of formal descriptions of the same standard in different
formal specification languages.
Rather than provide a mapping from all the concepts of ITU-T Rec. X.902 | ISO/IEC 10746-2, this Recommendation |
International Standard focuses on the most basic. A semantics for the higher level architectural concepts is provided
indirectly through their definition in terms of the basic ODP concepts.
Examples of the use of some of the formal specification languages in this report can be found in TR 10167 (Guidelines
for the Application of ESTELLE, LOTOS and SDL).
In the following clauses, the concepts are numbered in accordance with the scheme used in ITU-T Rec. X.902 |
This Recommendation | International Standard specifies an architectural semantics for ODP. This is required to:
? provide formalisation of the ODP modelling concepts;
? assist sound and uniform development of formal descriptions of standards for distributed systems;
? act as a bridge between the ODP modelling concepts and the semantic models of the specification
languages: LOTOS, SDL, ESTELLE and Z;
? provide a basis for uniform and consistent comparison between formal descriptions of the same standard
in specification languages that are used to develop an architectural semantics.
This part is normative.