The Technical Reference Model provides a taxonomy and visual representation of the structure of information systems, and in particular of the platform functions that support business applications.
It is important to bear in mind that the purpose of the Technical Reference Model is to aid the understanding of the taxonomy. It has no architectural significance beyond that goal.
Any technical reference model has two main components:
The objective of the TOGAF Technical Reference Model is to provide a widely accepted core taxonomy, and an appropriate visual representation of that taxonomy. The Technical Reference Model graphic is illustrated under The Technical Reference Model in Detail, and the taxonomy is explained under Application Platform - Taxonomy.
One of the great difficulties in developing an architectural framework is in choosing a technical reference model that works for everyone.
The TOGAF TRM was originally derived from the TAFIM TRM (which in turn was derived from the IEEE POSIX 1003.0 model - see Part IV, ISO/IEC 14252 (IEEE Std 1003.0), for details). This TRM is 'platform-centric': it focuses on the services and structure of the underlying platform necessary to support the use and reuse of applications (i.e., on application portability). In particular, it centers on the interfaces between that platform and the supported applications, and between the platform and the external environment.
The current TOGAF TRM is an amended version of the TAFIM TRM, which aims to emphasise the aspect of interoperability as well as that of portability.
The objective of the TRM is to enable structured definition of the standardized application platform and its associated interfaces. The other entities, which are needed in any specific architecture, are only addressed in the Technical Reference Model insofar as they influence the application platform. The underlying aim in this approach is to ensure that the higher level building blocks which make up business solutions have a complete, robust platform on which to run.
Other architectural models - taxonomies and/or graphics - not only are possible, but may be preferable for some organizations. For example, such an organization-specific model could be derived by extension or adaptation of the TOGAF TRM. Alternatively, a different taxonomy may be embodied in the legacy of previous architectural work by an organization, and the organization may prefer to perpetuate use of that taxonomy. Similarly, an organization may prefer to represent the TOGAF taxonomy (or its own taxonomy) using a different form of graphic, which better captures legacy concepts and proves easier for internal communication purposes.
Apart from the need to recognize that the structure embodied in the taxonomy is reflected in the structure of the Standards Information Base (so any organization adopting a different taxonomy will need to reflect its taxonomy in its own SIB), there is no problem with using other architectural taxonomies and/or graphics with TOGAF. The core of TOGAF is its Architecture Development Method: the TRM and the SIB are tools used in applying the ADM in the development of specific architectures. Provided consistency between TRM and SIB are maintained, the TOGAF ADM is valid whatever the choice of specific taxonomy, TRM graphic, or SIB toolset.
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