Capability Maturity Model
The Capability Maturity Model (CMM) is a method for evaluating and measuring the maturity of the software development process of organizations on a scale of 1 to 5. The CMM was developed by the Software Engineering Institute (SEI) at Carnegie Mellon University in Pittsburgh. It has been used extensively for avionics software and for government projects since it was created in the mid-1980s. The Software Engineering Institute has subsequently released a revised version known as the Capability Maturity Model Integration (CMMI).
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Levels of the CMM
(See chapter 2 of (March 2002 edition of CMMISM from SEI), page 11.)
There are 5 levels of the CMM. According to the SEI, "Predictability, effectiveness, and control of an organization's software processes are believed to improve as the organization moves up these five levels. While not rigorous, the empirical evidence to date supports this belief."
- 1 - Initial
- At maturity level 1, processes are usually ad hoc and chaotic. The organization usually does not provide a stable environment. Success in these organizations depends on the competence and heroics of the people in the organization and not on the use of proven processes. In spite of this ad hoc, chaotic environment, maturity level 1 organizations often produce products and services that work; however, they frequently exceed the budget and schedule of their projects.
- Maturity level 1 organizations are characterized by a tendency to over commit, abandon processes in the time of crisis, and not be able to repeat their past successes.
- 2 - Repeatable
- At maturity level 2, Software development successes are repeatable. The organization may use some basic project management to track cost and schedule.
- Process discipline helps ensure that existing practices are retained during times of stress. When these practices are in place, projects are performed and managed according to their documented plans.
- Project status and the delivery of services are visible to management at defined points (for example, at major milestones and at the completion of major tasks).
- 3 - Defined
- At maturity level 3, processes are well characterized and understood, and are described in standards, procedures, tools, and methods.
- The organization’s set of standard processes, which is the basis for level 3, is established and improved over time. These standard processes are used to establish consistency across the organization. Projects establish their defined processes by tailoring the organization’s set of standard processes according to tailoring guidelines.
- The organization’s management establishes process objectives based on the organization’s set of standard processes and ensures that these objectives are appropriately addressed.
- A critical distinction between level 2 and level 3 is the scope of standards, process descriptions, and procedures. At level 2, the standards, process descriptions, and procedures may be quite different in each specific instance of the process (for example, on a particular project). At level 3, the standards, process descriptions, and procedures for a project are tailored from the organization’s set of standard processes to suit a particular project or organizational unit.
- 4 - Managed
- Using precise measurements, management can effectively control the software development effort. In particular, management can identify ways to adjust and adapt the process to particular projects without measurable losses of quality or deviations from specifications.
- Subprocesses are selected that significantly contribute to overall process performance. These selected subprocesses are controlled using statistical and other quantitative techniques.
- A critical distinction between maturity level 3 and maturity level 4 is the predictability of process performance. At maturity level 4, the performance of processes is controlled using statistical and other quantitative techniques, and is quantitatively predictable. At maturity level 3, processes are only qualitatively predictable.
- 5 - Optimizing
- Maturity level 5 focuses on continually improving process performance through both incremental and innovative technological improvements. Quantitative process-improvement objectives for the organization are established, continually revised to reflect changing business objectives, and used as criteria in managing process improvement. The effects of deployed process improvements are measured and evaluated against the quantitative process-improvement objectives. Both the defined processes and the organization’s set of standard processes are targets of measurable improvement activities.
- Process improvements to address common causes of process variation and measurably improve the organization’s processes are identified, evaluated, and deployed.
- Optimizing processes that are agile and innovative depends on the participation of an empowered workforce aligned with the business values and objectives of the organization. The organization’s ability to rapidly respond to changes and opportunities is enhanced by finding ways to accelerate and share learning.
- A critical distinction between maturity level 4 and maturity level 5 is the type of process variation addressed. At maturity level 4, processes are concerned with addressing special causes of process variation and providing statistical predictability of the results. Though processes may produce predictable results, the results may be insufficient to achieve the established objectives. At maturity level 5, processes are concerned with addressing common causes of process variation and changing the process (that is, shifting the mean of the process performance) to improve process performance (while maintaining statistical predictability) to achieve the established quantitative process-improvement objectives.
Recent versions of CMMI from SEI indicate a "level 0", characterized as "Incomplete". Many observers leave this level out as redundant or unimportant, but Pressman and others make note of it. See page 18 of the August 2002 edition of CMMI from SEI (Note: PDF file).
Anthony Finkelstien extrapolated that negative levels, or the Capability Immaturity Model, are necessary to represent environments that are not only indifferent, but actively counterproductive, and this was refined by Tom Schorsch:
- CMM level 0 (negligent)
- CMM level -1 (obstructive)
- CMM level -2 (contemptuous)
- CMM level -3 (undermining)
Some praise of the CMM
- The CMM was developed to give Defense organizations a yardstick to assess and describe the capability of software contractors to provide software on time, within budget, and to acceptable standards. It has arguably been successful in this role, even reputedly causing some software salespeople to clamour for their organizations' software engineers/developers to "implement CMM."
- The CMM is intended to enable an assessment of an organization's maturity for software development. It is an important tool for outsourcing and exporting software development work. Economic development agencies in India, Ireland, Egypt, and elsewhere have praised the CMM for enabling them to be able to compete for US outsourcing contracts on an even footing. Whilst this may have been very positive for the employment of software engineers in emerging or Third World economies - notably in India during the early 2000s - it is regarded as having adversely affected the potential employment opportunities for software engineers in the developed economies - notably the USA and Europe. This outsourcing is a form of labor arbitrage which is similar to the movement of manufacturing of (for example) fashion clothing or Nike shoes to Third World economies with relatively cheap labor rates.
- It is reputed that IBM, Motorola, Logica, BT, and others have discovered the following:
- It takes 18 months on average to move up one SEI level, but it has been done in 8 (refer XXX? to substantiate this).
- Defect rates can be lowered from 1 per 1,000 lines of code (said to be typical of Microsoft and its peers) down to 1 per 1,000,000 lines - this is roughly Six Sigma quality; refer also relevant Deming references (NB: Deming was not a proponent of Six Sigma per se, and advised against the use of any slogans for process quality improvement).(refer XXX? to substantiate this)
- There is no specific evidence for shortening "time to market", but there is (refer XXX? to substantiate this) for increasing the accuracy of estimating completion date from 75% overruns on average at level 1, to plus or minus 2% at level 5.
- Data on productivity increases is more variable, but it is at least (refer XXX? to substantiate this) a doubling of productivity.
Some criticism of the CMM
- The CMM does not describe how to create an effective software development organization. The traits it measures are, in practice, very hard to develop in an organization, even though they are very easy to recognize.
- The CMM can seem to be overly bureaucratic, promoting process over substance. For example, for emphasizing predictability over service provided to end users. More commercially successful methodologies (for example, The Unified Development Process) have focused not on the capability of the organization to produce software to satisfy some other organization or a collectively-produced specification, but on the capability of organizations to satisfy specific end user "use cases" as per the Object Management Group's UML (Unified Modelling Language) approach.
- The CMM's division into levels could ignore the possibility that a single group may exhibit all of the behaviors and may change from behavior to behavior over time. There is also the rule that a group must move from step to step along the continuum of the CMM, and that it is not "allowed" by the CMM for a group to move from one to five without going through the intermediate steps.