Understanding Metamodeling Brain Henderson-Sellers   View Paper (PDF)   Return to Tutorials Abstract Metamodelling underpins the UML both directly and in terms of the UML Profile Mechanism. This tutorial starts by explaining why metamodelling is important in the UML context and then evaluates the various aspects of metamodelling that are known to cause both practitioners and researchers the most problems. We explore the pros and cons of strict versus loose metamodelling, the notions of physical versus logical "instance-of" relationships and the various flavours of the "is-a" relationship (which include instantiation and generalization). These ideas are then applied to the UML context directly in an evaluation of the extension mechanisms of the UML, particularly stereotypes, and illustrated directly in terms of the metamodels currently underpinning not only the UML but also, as further examples, the OMG SPEM model for process metamodelling. This information will then permit developers of UML profiles to more successfully utilise the metamodelling aspects and know on which occasions it is better not to use metamodeling, in addition to providing end users with a greater capability to utilize the UML extension mechanisms. ©2005 Association for Computing Machinery