Systematic process improvement using ISO 9001:2000 and CMMI

3.4 ISO TR 15504 43
• Defect Prevention (DP);
• Technology Change Management (TCM);
• Process Change Management (PCM).
3.4 ISO TR 15504
ISO TR 15504 [8] was written to provide a framework for conducting consistent
assessments of process capability that would ensure an acceptable level
of repeatability and reliability across various appraisal methods. It is intended
to harmonize various assessment models and methods [9]. TR 15504 has
both a reference model for software activities and a compatible embedded
model for use in process assessments. It includes guidance on using assessments
for process improvement and capability determination [10]. In its
original format, TR 15504 was written from the supplier organization’s point
of view. As of this writing, efforts are still under way to extend this aspect
to cover acquirer processes as well.
TR 15504 is compatible with several other standards, such as ISO
12207:1995 [11] and ISO 9001:1994. It is compatible with ISO 9001 in very
general terms because both standards espouse the need for quality assurance
in design, development, production, installation, and servicing of software
products. Compatibility with ISO 12207 is much deeper because ISO 12207
provides an overall framework for software life-cycle processes.
Chapter 2 briefly discussed the process improvement aspects of ISO TR
15504, focusing on Part 7. Figure 2.1 shows all nine parts of the standard.
Only Parts 2 and 3 are normative. All other parts are informative.
‘‘Part 5: Assessment Model,’’ called the exemplar model, is the most controversial
part of the standard. The standard assumes that there will be many
compliant models that satisfy, or map to, this reference model and thus may
be used for assessments in accordance with the requirements of Part 3.
Because Part 5 contains many details and elaboration of the mandatory
processes and associated base practices, it is often used as a guideline for
interpreting Part 2. Part 2 is a framework that allows assessments to use
different models, but it can not be used by itself to support an assessment.
Those models and methods must be mapped to the reference model to judge
their compatibility. The controversial aspect of Part 5 stems from its inclusion
in TR 15504 as an informative section. By publishing the assessment model
as an integral part of the standard, it may become a de facto standard, despite
being labeled informative. This then defeats the original intent of allowing
various models to be used in appraisals.