  This chapter discusses the current state of the art, and emerging research
challenges, for metamodelling. In the state-of-the-art review on metamodelling,
we review approaches, abstractions, and tools for metamodelling, evaluate them
with respect to their expressivity, investigate what role(s) metamodels may
play at run-time and how semantics can be assigned to metamodels and the domain
specific modeling languages they could define. In the emerging challenges
section on metamodelling we highlight research issues regarding the management
of complexity, consistency, and evolution of metamodels, and how the semantics
of metamodels impacts each of these.
