Specification of Reactive Hardware/Software Systems - Electronic ...

120 Concepts for the Integration of Specification and Design
Module G
Module A Module B Module C Module D
Figure 5.1: Architecture with Bus Structure
Module G
Module A Module B Module C Module D
Figure 5.2: Architecture with Star Structure
Considerations about the ’distribution of intelligence’ (centralised / decentralised) may
have a major influence on the communication between the collaborating processes. An
Architecture Structure Diagram such as Figure 5.1 can be used to open a discussion
about the distribution issue. A distribution of intelligence means that relatively simple
messages from a central module can cause complex actions of decentralised modules.
An elegant solution for such a model is defining a dedicated command language for the
communication on the channel. Another solution is the selection of an (standardised)
industrial network solution. Both solutions imply that some conceptual solution is chosen.
This shows that architecture design is related to conceptual solution selection. It will be
clear that such choices have a strong influence on the modelling of the communication
between collaborating objects and clusters. This example shows again that functional
behaviour and architecture are intertwined, and must be performed concurrently to
prevent costly iterations. This is confirmed by [SB82].
5.2.5 Mapping
One of the key issues in SHE is the mapping of architecture design upon objects, clusters
and channels. Architecture must be formalised into a behaviour specification. We offer
the concept of boundaries (to be introduced in Section 5.8) as an intermediate to perform