  Even though modern service-oriented and data-oriented architectures promise
to deliver loosely coupled control systems, they are inherently brittle as they
commonly depend on a priori agreed interfaces and data models. At the same
time, the Semantic Web and a whole set of accompanying standards and tools are
emerging, advocating ontologies as the basis for knowledge exchange. In this
paper we aim to identify a number of key ideas from the myriad of
knowledge-based practices that can readily be implemented by control systems
today. We demonstrate with a practical example (a three-channel imager for the
Mercator Telescope) how ontologies developed in the Web Ontology Language (OWL)
can serve as a meta-model for our instrument, covering as many engineering
aspects of the project as needed. We show how a concrete system model can be
built on top of this meta-model via a set of Domain Specific Languages (DSLs),
supporting both formal verification and the generation of software and
documentation artifacts. Finally we reason how the available semantics can be
exposed at run-time by adding a "semantic layer" that can be browsed, queried,
monitored etc. by any OPC UA-enabled client.
