Modelling languages such as the Unified Modeling Language are used during the early phases of system development to capture
requirements and to express high-level designs. Many such languages have no universally fixed interpretations since different
development projects often use key concepts, like Class, Generalization and Association, in slightly different ways. Therefore
meta-modelling, i.e. the precise specification of the concepts used in a model, is of importance in order to avoid misunderstandings.
The Boom framework, presented in this paper, is intended for this kind of meta-modelling. The framework consists of a collection of
modelling constructs specified with a small object-oriented language. The framework is simple enough for an engineer to adjust
the modelling concepts to project specific needs. It includes all necessary aspects of language specification, among them
definition of abstract syntax, well-formedness rules, and dynamic semantics. To demonstrate its use, this paper includes a
specification of some of the constructs defined in the Unified Modeling Language.