modularity

PLanCompS (Programming Language Components and Specifications, since 2011) is an open international collaboration, continuing from an EPSRC-funded research project (2011-16).

CBS (Component-Based Semantics, since 2004) is a framework and meta-language for component-based specification of programming languages.

MSOS (Modular SOS, 1999–2016) is modular variant of SOS (structural operational semantics).

Action Semantics (1985–2005) is a hybrid of denotational and operational semantics, developed in collaboration with David Watt (Glasgow).