  When a processing unit relies on data from external streams, we may face the
problem that the stream data needs to be rearranged in a way that allows the
unit to perform its task(s). On arrival of new data, we must decide whether
there is sufficient information available to start processing or whether to
wait for more data. Furthermore, we need to ensure that the data meets the
input specification of the processing step. In the case of multiple input
streams it is also necessary to coordinate which data from which incoming
stream should form the input of the next process instantiation. In this work,
we propose a declarative approach as an interface between multiple streams and
a processing unit. The idea is to specify via answer-set programming how to
arrange incoming data in packages that are suitable as input for subsequent
processing. Our approach is intended for use in asynchronous multi-context
systems (aMCSs), a recently proposed framework for loose coupling of knowledge
representation formalisms that allows for online reasoning in a dynamic
environment. Contexts in aMCSs process data streams from external sources and
other contexts.
