Capability Maturity Model

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The Capability Maturity Model (CMM) is a service mark owned by Carnegie Mellon University (CMU) and refers to a development model elicited from actual data. The data was collected from organizations that contracted with the U.S. Department of Defense, who funded the research, and they became the foundation from which CMU created the Software Engineering Institute (SEI). Like any model, it is an abstraction of an existing system. Unlike many that are derived in academia, this model is based on observation rather than on theory.

When it is applied to an existing organization's software development processes, it allows an effective approach toward improving them. Eventually it became clear that the model could be applied to other processes. This gave rise to a more general concept that is applied to business processes and to developing people.


The Capability Maturity Model (CMM) was originally developed as a tool for objectively assessing the ability of government contractors' processes to perform a contracted software project. The CMM is based on the process maturity framework first described in the 1989 book Managing the Software Process by Watts Humphrey. It was later published in a report in 1993 (Technical Report CMU/SEI-93-TR-024 ESC-TR-93-177 February 1993, Capability Maturity Model SM for Software, Version 1.1) and as a book by the same authors in 1995.

Though the CMM comes from the field of software development, it is used as a general model to aid in improving organizational business processes in diverse areas; for example in software engineering, system engineering, project management, software maintenance, risk management, system acquisition, information technology (IT), services, business processes generally, and human capital management. The CMM has been used extensively worldwide in government, commerce, industry and software development organizations.

The development of CMM at SEI

Active development of the model by the US Department of Defense Software Engineering Institute (SEI) began in 1986 when Humphrey joined the Software Engineering Institute located at Carnegie Mellon University in Pittsburgh, Pennsylvania after retiring from IBM. At the request of the U.S. Air Force he began formalizing his Process Maturity Framework to aid the U.S. Department of Defense in evaluating the capability of software contractors as part of awarding contracts.

The result of the Air Force study was a model for the military to use as an objective evaluation of software subcontractors' process capability maturity. Humphrey based this framework on the earlier Quality Management Maturity Grid developed by Philip B. Crosby in his book "Quality Is Free". However, Humphrey's approach differed because of his unique insight that organizations mature their processes in stages based on solving process problems in a specific order. Humphrey based his approach on the staged evolution of a system of software development practices within an organization, rather than measuring the maturity of each separate development process independently. The CMM has thus been used by different organizations as a general and powerful tool for understanding and then improving general business process performance. Watts Humphrey's Capability Maturity Model (CMM) was published in 1988.

Organizations were originally assessed using a process maturity questionnaire and a Software Capability Evaluation method devised by Humphrey and his colleagues at the Software Engineering Institute (SEI).

CMM is superseded by CMMI

The CMM model proved useful to many organizations, but its application in software development has sometimes been problematic. Applying multiple models that are not integrated within and across an organization could be costly in terms of training, appraisals, and improvement activities. The Capability Maturity Model Integration (CMMI) project was formed to sort out the problem of using multiple CMMs.

For software development processes, the CMM has been superseded by Capability Maturity Model Integration (CMMI), though the CMM continues to be a general theoretical process capability model used in the public domain.

CMM is adapted to processes other than software development

The CMM was originally intended as a tool to evaluate the ability of government contractors to perform a contracted software project. Though it comes from the area of software development, it can be, has been, and continues to be widely applied as a general model of the maturity of processes (e.g., IT Service Management processes) in IS/IT (and other) organizations.

Capability Maturity Model topics

Maturity model

A maturity model can be described as a structured collection of elements that describe certain aspects of maturity in an organization. A maturity model may provide, for example :

  • a place to start
  • the benefit of a community’s prior experiences
  • a common language and a shared vision
  • a framework for prioritizing actions
  • a way to define what improvement means for your organization.

A maturity model can be used as a benchmark for comparison and as an aid to understanding - for example, for comparative assessment of different organizations where there is something in common that can be used as a basis for comparison. In the case of the CMM, for example, the basis for comparison would be the organizations' software development processes.

Capability Maturity Model structure

The Capability Maturity Model involves the following aspects:

  • Maturity Levels: a 5-Level process maturity continuum - where the uppermost (5th) level is a notional ideal state where processes would be systematically managed by a combination of process optimization and continuous process improvement.
  • Key Process Areas: a Key Process Area (KPA) identifies a cluster of related activities that, when performed collectively, achieve a set of goals considered important.
  • Goals: the goals of a key process area summarize the states that must exist for that key process area to have been implemented in an effective and lasting way. The extent to which the goals have been accomplished is an indicator of how much capability the organization has established at that maturity level. The goals signify the scope, boundaries, and intent of each key process area.
  • Common Features: common features include practices that implement and institutionalize a key process area. There are five types of common features: commitment to Perform, Ability to Perform, Activities Performed, Measurement and Analysis, and Verifying Implementation.
  • Key Practices: The key practices describe the elements of infrastructure and practice that contribute most effectively to the implementation and institutionalization of the KPAs.

Levels of the Capability Maturity Model

There are five levels defined along the continuum of the CMM, and, 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 (chaotic, ad hoc, individual heroics) - the starting point for use of a new process.
  2. Managed - the process is managed according to the metrics described in the Defined stage.
  3. Defined - the process is defined/confirmed as a standard business process, and decomposed to levels 0, 1 and 2 (the latter being Work Instructions).
  4. Quantitatively managed
  5. Optimized - process management includes deliberate process optimization/improvement.

Within each of these maturity levels are Key Process Areas (KPAs) which characterize that level, and for each KPA there are five definitions identified:

  1. Goals
  2. Commitment
  3. Ability
  4. Measurement
  5. Verification

The KPAs are not necessarily unique to CMM, representing — as they do — the stages that organizations must go through on the way to becoming mature.

The CMM provides a theoretical continuum along which process maturity can be developed incrementally from one level to the next. Skipping levels is not allowed/feasible.

N.B.: The CMM was originally intended as a tool to evaluate the ability of government contractors to perform a contracted software project. It has been used for and may be suited to that purpose, but critics pointed out that process maturity according to the CMM was not necessarily mandatory for successful software development. There were/are real-life examples where the CMM was arguably irrelevant to successful software development, and these examples include many Shrinkwrap companies (also called commercial-off-the-shelf or "COTS" firms or software package firms). Such firms would have included, for example, Claris, Apple, Symantec, Microsoft, and Lotus. Though these companies may have successfully developed their software, they would not necessarily have considered or defined or managed their processes as the CMM described as level 3 or above, and so would have fitted level 1 or 2 of the model. This did not - on the face of it - frustrate the successful development of their software.

Level 1 - Initial (Chaotic)
It is characteristic of processes at this level that they are (typically) undocumented and in a state of dynamic change, tending to be driven in an ad hoc, uncontrolled and reactive manner by users or events. This provides a chaotic or unstable environment for the processes.
Level 2 - Repeatable
It is characteristic of processes at this level that some processes are repeatable, possibly with consistent results. Process discipline is unlikely to be rigorous, but where it exists it may help to ensure that existing processes are maintained during times of stress.
Level 3 - Defined
It is characteristic of processes at this level that there are sets of defined and documented standard processes established and subject to some degree of improvement over time. These standard processes are in place (i.e., they are the AS-IS processes) and used to establish consistency of process performance across the organization.
Level 4 - Managed
It is characteristic of processes at this level that, using process metrics, management can effectively control the AS-IS process (e.g., for software development ). In particular, management can identify ways to adjust and adapt the process to particular projects without measurable losses of quality or deviations from specifications. Process Capability is established from this level.
Level 5 - Optimized
It is a characteristic of processes at this level that the focus is on continually improving process performance through both incremental and innovative technological changes/improvements.

At maturity level 5, processes are concerned with addressing statistical common causes of process variation and changing the process (for example, to shift the mean of the process performance) to improve process performance. This would be done at the same time as maintaining the likelihood of achieving the established quantitative process-improvement objectives.

Software process framework for SEI's Capability Maturity Model

The software process framework documented is intended to guide those wishing to assess an organization/projects consistency with the CMM. For each maturity level there are five checklist types:

TypeSD Description
Policy Describes the policy contents and KPA goals recommended by the CMM.
Standard Describes the recommended content of select work products described in the CMM.
Process Describes the process information content recommended by the CMM. The process checklists are further refined into checklists for:
  • roles
  • entry criteria
  • inputs
  • activities
  • outputs
  • exit criteria
  • reviews and audits
  • work products managed and controlled
  • measurements
  • documented procedures
  • training
  • tools
Procedure Describes the recommended content of documented procedures described in the CMM.
Level overview Provides an overview of an entire maturity level. The level overview checklists are further refined into checklists for:
  • KPA purposes (Key Process Areas)
  • KPA Goals
  • policies
  • standards
  • process descriptions
  • procedures
  • training
  • tools
  • reviews and audits
  • work products managed and controlled
  • measurements

See also

External links