Software process definition is fundamental to achieving higher SEI CMM maturity levels. This section discusses applying the organization's software process definition, as described in this Guidebook, to individual projects.
At the organizational level, the standard software process is formally described, managed, controlled, and improved. At the project level, the emphasis is on the tailoring and usability of the organization's defined software process, and the value it adds to the project. This Guidebook describes the fundamental elements that each project involved in software development is expected to incorporate into its defined software process. The Guidebook also describes the relationships (e.g., ordering and interfaces) among these software process elements. It establishes a consistent method of performing the defined software activities across the organization, which is essential for long-term stability and improvement. Figure 1.2-1 (modified from the SEI CMM) depicts the relationship between this Guidebook and projects involving software engineering.
Each project has its own system requirements, constraints, and resources. Some of those requirements are allocated to software. To accommodate these requirements, constraints, and resources, the project software manager may tailor the activities in this Guidebook, using the guidelines in the Software Management Volume. The project software manager selects a software life cycle, and then develops the project's defined software process by tailoring the organization's standard software process for the project, and documenting the tailoring according to the guidance in activity 1.1.1.3 Define Software Development Process and its subactivities. The project's defined software process is documented in the Software Development Plan (SDP).
This Guidebook is not meant to be a substitute for a project's SDP which integrates an organization's standard software process into a project's defined software process.
Figure 1.2-1 Conceptual Software Process Framework Used In The Organization
(modified from the SEI CMM)
When the project is completed, its software products and lessons learned are placed in the software asset library for reuse or as a references for future software projects. Software metrics are collected and stored in the metrics database.
Having common standards, methodologies, and formats for software products (as defined throughout this Guidebook) on multiple projects makes software reuse more feasible. Reusing software products enables a project to reduce development time and cost, and supports long-term stability and process improvement. Reuse also reduces the overall risk on a project because the cost and effort of reusing a component that was used and tested in the same domain can be better anticipated.
The processes shown in Figure 1.2-1 are described in activities in this Guidebook, and are depicted graphically with Integration Definition (IDEF0) Method diagrams (see Section 5 of this Introduction for IDEF0 descriptions). Each process also is documented as a separate activity in the format described in Section 4 of this Introduction. This format enables the reader to easily navigate through the Guidebook, and makes the Guidebook a training tool for individuals unfamiliar with the organization's standard software process (see Figure 1.2-1). Although this Guidebook lays the basic foundation, applying the organization's standard software process does not guarantee a project's success. This Guidebook should be used as a reference and basic standard. Each project will encounter its own problems and conflicts, which are not always foreseeable. However, only through developing standard software processes, record keeping, and ongoing process improvement (see activity 4.1 Identify And Test Process Improvements) will the organization begin identifying trouble spots particular to its domain, and taking corrective actions to prevent or reduce the risk of problems occurring. A standard software process enables the organization to avoid repeating mistakes and fully use lessons learned (see activity 4.1.2 Identify Lessons Learned) from previous projects.
The processes documented in activities in this Guidebook reflect SEI CMM Levels 2 and 3. At these levels, organizations have institutionalized effective processes for managing software that can be repeated in future projects. These processes integrate software engineering and management activities.
In addition, the processes/activities in this Guidebook are based in part on the requirements and outline of MIL-STD-498 (approved 5 December 1994). This standard was selected over MIL-STD-2167A for multiple reasons, which include the following:
The majority of the Data Item Descriptions (DID) described and discussed throughout this Guidebook are based upon MIL-STD-498 (see Appendix E for the DIDs).