Object-oriented design pattern for DSL program monitoring

To ease domain-specific language (DSL) development, a range of language workbenches have been created, which provide language design facilities and programming tools, like editors and validators. In spite of these developments, there is a perceived lack of tool support for execution monitoring, which is the basic block for program validation and maintenance. To partially address this issue some language workbenches offer ad-hoc solutions for DSL debugging, but lack support for other monitoring features. In the literature, a number of domain-specific monitoring tools have been proposed. However, there is no clear way for integrating these developments in existing language workbenches. This paper presents ten requirements needed for creating a modular and composable DSL monitoring infrastructure and proposes an object-oriented design pattern for DSL program monitoring. This pattern provides a practical answer to the problem of interfacing the runtime of a DSL with concrete domain-specific monitoring tools. To show the practicability of our approach, we add monitoring support to a simple lambda calculus, without changing the standard interpreter. The ease of integrating monitoring tools is shown through the development of a tracer and the integration of an off-the-shelf domain-specific profiler.