| Abstract: |
Composability and compositionality are well recognised as key enablers in rigorous design and analysis of complex systems. We argue that existing work on these enablers, specific to real-time
systems, has exclusively focussed on design and analysis of structural composition, by which we refer to composition of either separate software tasks or compositions thereof on a shared platform
such as a processor. Though structural composition is common and likely the most useful such composition, we make the case of an altogether different kind of composition which we refer to as
behavioural composition. As a specific example of behavioural composition, we discuss how to constructively build complex server algorithms, called Demand Bound Servers (DBS), by composing
constituent simpler server algorithms, even hierarchically. As a result of such composition, we can build server algorithms to more tightly match the requirements of tasks they need to serve,
which indeed is not possible with the simpler components themselves. This is an example of how new behaviour is emergent out of the composition. We remain curious if there are other such examples
of behavioural composition of interest to real-time systems. |
