At ASML the ASOME data modelling language has been defined. Many system designers are defining models in this language, and the question is whether there is an easy way to assess that these models are ok. This can be done using metrics. The question is which metrics are proper. In this MSc research various metrics from different sources are collected. The suitability of these metrics to indicate the complexity and maintainability of the models is assessed by questionaires and qualitative interviews.