Component-Based Description of Programming Languages

Research in formal description of programming languages over the past four decades has led to some significant achievements. These include formal syntax and semantics for complete major programming languages, and theoretical foundations for novel features that might be included in future languages. Nevertheless, to give a completely formal, validated description of any significant programming language using the conventional frameworks remains an immense effort, disproportionate to its perceived benefits. Our diagnosis of the causes of this disappointing situation highlights two major deficiencies in the pragmatic aspects of formal language descriptions in conventional frameworks: lack of reusable components, and poor tool support. Part of the proposed remedy is a radical shift to a novel component-based paradigm for the development of complete language descriptions, based on simple interfaces between descriptions of syntactic and semantic aspects, and employing frameworks that allow independent description of individual programming constructs. The introduction of a language-independent notation for common programming constructs maximises the reusability of components. Tool support for component-based language description is being developed using the ASF+SDF Meta-Environment; the aim is to provide an efficient component-based workbench for use in design and implementation of future programming languages, accompanied by an online repository for validated formal descriptions of programming constructs and languages.