|In order to set up the context of some terms and concepts mentioned in the Process Web Center, the following working definitions, compiled from the literature are introduced.
Process (see also different views of definitions in the
Glossary) is a partially ordered set of activities performed by roles to achieve a software product/artefact and intermediate products. Basically, a process is carried out in three basic phases: process modelling, process instantiation (tailoring) and process execution (enactment) /Garg, 1996/.
Figure Intro 5: Simplified version of process phases
Process modelling (see also different publication on
process modelling) aims to represent the software development process as a coherent set of related steps. Explicitly modelling the software development is a significant progress in evolving the current state of software development practice from an applied art to an engineering discipline. The person in charge of modelling the process may use some reference models to produce the desired process model instead of starting the construction from scratch. Numerous organisations created their own reference model. Some reference models are defined in standards such as the ISO 12207 /ISO 12207, 1995/, IEEE 1220 /IEEE 1220, 1994/ and GD 250 also know as V-Model /VM 1997/ . Other reference models, are for internal use in a specific institution. In many cases, the adoption of the "particular" reference models among other external companies is so extensive that these models become a sort of standard status. For example, the PSS-05 /ESA, 1991/ from the European Space Agency (ESA) and the AQAP-150 /AQAP-150/ from the North Atlantic Treat Organisation (NATO). The process modeller may use the available process modelling languages to model the process. The chapter "Process Modelling Languages" written by Reidar Conradi and Letizia Jaccheri in /Derniame, 1998/ provide a detailed comparison among them.
Process instantiation and tailoring (see also different views of definitions in the
Glossary) comprise the instantiation and customisation of the available process models into a project-specific process. Some standards like GD250 define tailoring as the act of eliminating the (sub-)activities and artefacts from the reference model which are not relevant for a specific project. Hence, it does not consider the creation of new (sub-)activities. Tailoring is not a trivial task. It requires an comprehensive knowledge of the process model and the context of the real-world project. Another issue during this phase is to maintain the consistency of the process after tailoring.
The process execution and enactment phase (see also different views of definitions in the
Glossary) concern the execution of the activities defined in the process to produce the target software product. Some process engines support (semi-)automatic process enactment. The enactment of the activities modifies the state of the artefacts.