Higher-level modelling is considered to be the answer to many of the problems computer science is faced with. In order to do modelling, it is necessary to use proper tools. This article is about modelling tools and how they can be generated automatically out of (modelling) language descriptions. Language descriptions in turn are given in meta-models. In this article, we define a terminology for aspects of meta-models and check how they are supported by existing meta-modelling tools. In particular we look at semantic aspects of the meta-models.