ISO 15504 AND CMMI



ISO 15504 and CMMI

ISO 15504 and CMMI



Introduction

Improving software processes is by now recognized as an important endeavour for software organizations. A commonly used paradigm for improving software engineering practices is the benchmarking paradigm (Rubin 2008 79-84). Such best practices are commonly codified in an assessment model, like the SW-CMM 1 or the emerging ISO/IEC 15504 international standard. These assessment models also order the practices in a recommended sequence of implementation, hence providing a predefined improvement path.

Improvement following the benchmarking paradigm almost always involves a software process assessment (SPA).3 An SPA provides a quantitative score reflecting the extent of an organization's or project's implementation of the best practices defined in the assessment model. The emerging ISO/IEC 15504 international standard is an attempt to harmonize the existing assessment models that are in common use. It defines a scheme for measuring the capability of software processes. A basic premise of 15504 is that the quantitative score from the assessment is associated with the performance of the organization or project.

Background

A recent survey of assessment sponsors found that baselining process capability and tracking process improvement progress are two important reasons for conducting an SPA (Butler 2005 14-17). Both of these reasons rely on the quantitative score obtained from an assessment, indicating that sponsors perceive assessments as a measurement procedure.

As with any measurement procedure, its validity must be demonstrated before one has confidence in its use. The validity of measurement is defined as the extent to which a measurement procedure is measuring what it is purporting to measure (Wynekoop and Russo 2003 181-190). During the process of validating a measurement procedure one attempts to collect evidence to support the types of inferences that are to be drawn from measurement scores (El Emam Drouin Melo 2008 69-114).

Theoretical basis for validating software development process capability

The SW-CMM defines 18 KPAs that are believed to represent good software engineering practices (Software Engineering Institute, 1995). The main design, construction, integration, and testing processes are embodied in the Software Product Engineering KPA (Software Engineering Institute, 1998a). This is defined at Level 3.

As organizations increase their organizational process capability by implementing progressively more of these processes, it is hypothesized that three types of benefits will accrue:

the differences between targeted results and actual results will decrease across projects,

the variability of actual results around targeted results decreases, and

Costs decrease, development time shortens, and productivity and quality increase.

However, these benefits are not posited only for the Software Product Engineering KPA, but rather as a consequence of implementing combinations of practices. The emerging ISO/IEC 15504 international standard, on the other hand, defines a set of processes, and a scale that can be used to evaluate the capability of each process separately (Krasner 1999 632-703). The initial requirements for ISO/IEC 15504 state that an organization's assessment results should reflect its ability to achieve productivity and/or development cycle time goals.

The Software Engineering Institute has published a so-called Technology Reference Guide, which is a collection and classification of software ...