Coverage of the Bodies of Knowledge
The intent of CMMI is to provide a CMM that covers product and service development and maintenance but also provides an extensible framework so that new bodies of knowledge can be added. Currently, four bodies of knowledge are available to you when planning process improvement using CMMI:
Integrated product and process development
This text refers to these bodies of knowledge as "disciplines." In other words, when we refer to selecting a "discipline," it can be one of the bodies of knowledge listed above. Other bodies of knowledge may be integrated into the CMMI Framework in the future; however, none are planned at this time.
Systems engineering covers the development of total systems, which may or may not include software. Systems engineers focus on transforming customers' needs, expectations, and constraints into products and supporting these products throughout their life.
Software engineering covers the development of software systems. Software engineers focus on applying systematic, disciplined, and quantifiable approaches to the development, operation, and maintenance of software.
Integrated Product and Process Development
Integrated product and process development (IPPD) is a systematic approach that achieves a timely collaboration of relevant stakeholders throughout the life of the product to satisfy customers' needs, expectations, and requirements. The processes to support an IPPD approach are integrated with the other processes in the organization.
If a project or organization chooses IPPD, it performs the IPPD best practices concurrently with other best practices used to produce products (e.g., those related to systems engineering). That is, if an organization or project wishes to use IPPD, it must select one or more disciplines in addition to IPPD.
As work efforts become more complex, project managers may use suppliers to perform functions or add modifications to products that are specifically needed by the project. When those activities are critical, the project benefits from enhanced source analysis and from monitoring supplier activities before product delivery. Under these circumstances, the supplier sourcing discipline covers the acquisition of products from suppliers
Similar to IPPD best practices, supplier sourcing best practices must be selected in conjunction with best practices used to produce products.