Source code annotations as formal languages

Attribute-oriented programming (source code annotations) is a program level marking technique that enables enrichment of program elements with custom metadata. In this paper we hypothesize that there is a correspondence between source code annotations and conventional formal languages in general. We analyze our observations about source code annotations from three aspects of language description: concrete syntax, abstract syntax, and semantics. The discussion provides evidence of the hypothesized correspondence and we use it as a basis for our definition of an annotation-based language (abbreviated: @L). However, the analysis also shows that compared to conventional formal languages, source code annotations have some specificities mainly connected to their binding to host program elements. The presented analysis contributes to the field of attribute-oriented programming by discussing the relationship between annotations and conventional formal languages, and by surveying relational idioms in annotations' usage that can be inspirational for annotations' authors.