Achieving reusability in KMOS instrument software through design patterns

KMOS is a near-infrared multi-object spectrometer, which is currently being built by a British-German consortium for the ESO VLT. As for any other VLT instrument, the KMOS instrument software is based on the application framework given by the VLT Common Software, but faces particular design challenges in addition. As separate parts of the software require a similar functionality with respect to mechanical and optical permissibility checks, user interface, and configuration control, a number of tasks have to be implemented twice and slightly differently. It turns out that most of these issues can be tackled successfully by means of well-known object-oriented design patterns, providing for reusability and improving the overall software design. We present a set of sample problems along with their particular pattern solution.