  Predicate-based communication allows components of a system to send messages
and requests to ensembles of components that are determined at execution time
through the evaluation of a predicate, in a multicast fashion. Predicate-based
communication can greatly simplify the programming of autonomous and adaptive
systems. We present a stochastically timed extension of the Software Component
Ensemble Language (SCEL) that was introduced in previous work. Such an
extension raises a number of non-trivial design and formal semantics issues
with different options as possible solutions at different levels of
abstraction. We discuss four of these options, of which two in more detail. We
provide a formal semantics definition and an illustration of the use of the
language modeling a bike sharing system, together with some preliminary
analysis of the system performance.
