Composing Structural Views in xADL

Experience with building an architecture for an industrial Automatic Guided Vehicle Transportation System (AGVTS) shows that several essential concerns crosscut the architectural views. To cope with this, a stronger separation proved to be necessary, i.e. using different views for different concerns. In practice this was difficult, since the support for relations between views is very limited. This makes separation of concerns in views hard, thereby increasing maintenance overhead and reducing reuse capabilities. Our claim is that specifying compositions of views is as important as specifying the views itself. This paper extends a representative architectural description language (xADL) which support for composing structural views, by introducing three relations, namely refinement, mapping, and unification. Improving separation of concerns in views and their explicit composition enhances architecture understandability and changeability. The feasibility of the relations is assessed by redesigning the AGVTS architecture. Based on a real maintenance scenario, we investigate to what extent these explicit compositions lead (or not) to enhanced architectural changeability for evolving the distribution strategy in the AGVTS system.