The abstract syntax of UML is specified using the Meta-Object Facility (MOF) metamodel. MOF is a
modeling language that provides a meta-meta-model at the top layer of the four-layer metadata
architecture, which is used to define the metamodels, like the UML. The MOF specification defines
the structure and semantics for constructing metamodels, including the UML. By using MOF, UML
ensures that its structure is well-defined and can be processed by tools that understand MOF-based
metamodels. The use of MOF to specify UML abstract syntax ensures a clear, structured, and
standardized method of describing the semantics of UML components, enabling consistent
interpretation and implementation across different modeling tools and environments.
