How to keep domain requirements models reasonably sized

A domain model based requirements engineering approach has proven to be helpful when developing softwareintensive, embedded control systems. A typical characteristic of this domain is the high volatility of ideas resulting in frequent innovations. Thus, aside from evolution from external research, the innovative projects at small and mediumsized enterprises (SMEs) are the main sources for suitable domain model changes. In this paper we describe how changes (reductions and extensions) to the domain model can be derived from experiences with finalised projects at an SME. The overall goal is to make the domain model most valuable by keeping it at a reasonable size: neither too big nor too small. Unnecessary ballast will be removed and frequently modelled extensions will be added. We outline corresponding tool support but emphasise that the engineer still must remain in the loop.