Model Tailoring | CMMI (c) Guidelines for Process Integration and Product Improvement

Tailoring^[2] a CMMI model is a process whereby only a subset of a model is used to suit the needs of a specific domain of application. Model tailoring should be done cautiously and an organization should be aware that it can result in significant gaps in efforts to improve or appraise an organization's or a project's capabilities.

^[2] The tailoring discussed in this section does not address adaptation of an organization's set of standard processes for use on a specific project. Such tailoring is driven by tailoring guidelines defined in this book's glossary.

Tailoring of a CMMI model can be viewed from two perspectives:

Model tailoring for process improvement
Model tailoring for benchmarking

Many organizations will use a CMMI model for benchmarking as well as process improvement. Such tailoring is constrained by the intersection of criteria outlined in the next two sections.

Tailoring Constraints for Process Improvement

For internal process improvement, it is appropriate to restrict or expand the scope of an organization's or project's improvement effort (including appraisals). The tailoring may address individual disciplines, process areas, maturity levels, and/or capability levels. The tailoring of a model should focus on identifying the process areas and practices that support an organization's business needs and objectives.

Care must be taken when considering whether to exclude portions of a CMMI model. Given a CMMI model's focus on the essential characteristics of an effective process, the majority of the process areas and practices in a model should be addressed.

Organizations and projects implementing less than a full set of process areas, goals, or practices can still achieve significant value from a CMMI model. However, because of the interrelationship of model components, exclusion of process areas, goals, or practices may diminish the benefits. The wholesale exclusion of fundamental process areas or specific practices defeats the purpose of process improvement.

Goals cannot be excluded from the process areas included in the scope of a process improvement effort. Goals reflect the minimum requirements for satisfying a process area. Goals work together to support a process area and may not be individually designated as "not applicable."

Tailoring a model also affects comparability of process improvement efforts undertaken by different projects. If one project excludes parts of a model and the other excludes other parts of the same model, the degree of comparability of results is reduced.

Tailoring Constraints for Benchmarking

Using CMMI for benchmarking allows an organization to compare its appraisal results to other organizations. Comparison to competitors is aided by state-of-the-practice reports. Appraisal results can also be used to compare a group of organizations such as potential suppliers. Tailoring a CMMI model used for such benchmarking is extremely dependent on how closely each organization follows the complete collection of process areas, goals, and practices.

Realistically, benchmarking is possible only when the results of an appraisal can be expressed as a maturity level. Until such time that achievement profiles (results of the continuous representation) are publicly shared, the value of benchmarking is found in the maturity level rating. A maturity level rating can be achieved directly using the staged representation. Such a rating can also be achieved using the continuous representation by the extra step of employing equivalent staging to convert the achievement profile to a maturity level.

The maturity level ratings resulting from the use of models in multiple appraisals is useful only to the extent that there is consistency of use among the organizations being compared. Consequently, model tailoring for benchmarking is significantly constrained, especially where maturity levels resulting from appraisals are disseminated publicly.

The scope of the organization chosen for an appraisal affects the usefulness of benchmarking. If one organization chooses to appraise only the software engineering function while another chooses to appraise both software and systems engineering functions, comparing the two would not be fair or accurate even if they implemented all of the same CMMI process areas, goals, and practices.

Planning Tailoring for Benchmarking

There are some issues to consider well in advance of planning to have an appraisal conducted. The way you construct your process improvement program will affect how easily you can achieve a rating that is meaningful to your organization.

Process Areas' Appraisal Scope

Process areas cannot be excluded except to omit process areas that are outside of the scope of an appraisal. For example, an organization using a staged representation can exclude process areas at maturity levels 4 and 5 when the organization is focused on achieving maturity level 3.

An organization using a continuous representation can exclude process areas outside the scope of the target profile; however, benchmarking opportunities using the continuous representation are possible only through the use of equivalent staging, so careful analysis should be used before deciding to exclude a process area.

Not Applicable

Process areas can be excluded when they are determined to be not applicable to the organization being appraised. This means that goals and practices of the process area are inherently outside of the organization's scope of work. For example, if an organization does not use suppliers for products or services critical to its product development efforts, it can exclude Supplier Agreement Management from its appraisal.

Under these circumstances, a maturity level rating could still be determined; however, that maturity level rating must also state which process areas were considered not applicable.

Not Rated

A process area is designated "not rated" if it is outside the appraisal scope or if insufficient data is available to satisfy the data-coverage criteria. A maturity level cannot be determined if process areas at that maturity level (or below) are not rated. In other words, "not rated" process areas are interpreted as not achieved and act against the achievement of a maturity level.

Goals

Specific goals and generic goals cannot be excluded from process areas included in the scope of an appraisal effort. Goals reflect the minimum requirements for satisfying a process area. If a process area is applicable, each of its specific goals is applicable as well as the generic goals within the scope of the appraisal.

Practices

Specific practices and generic practices are typical activities necessary to implement and institutionalize the goals of the process area. Therefore, appropriate alternative practices can be substituted for specific practices and generic practices if the alternatives are effective in implementing and institutionalizing the goals.

Informative Components

All other model components (subpractices, typical work products, examples, amplifications, elaborations, and references) are informative and can be excluded at will.