The history of programming languages shows a progressive development from low-level programming languages close to the machine, to high-level languages close to the problems being solved with software. Domain-specific languages take this a step further than general purpose programming languages by making assumptions about the class of applications for which the language is intended. Complete applications typically require programs in multiple (technical) domains, which can be catered for by separate domain-specific languages. While such separation of concerns is beneficial for domain expressivity, it often leads to loose coupling and lack of static verification. Hence, the design of individual DSLs needs to be complemented with their linguistic integration.
In this talk, I illustrate these ideas with the design of WebDSL, a domain-specific language for data centric web applications. WebDSL linguistically integrates the definition of data models, user interfaces, actions, access control rules, data validation rules, styling rules, and workflow definitions. While maintaining separation between these concerns through specialized sub-languages, linguistic integration ensures static consistency checking and correct code generation. The language allows developers to concentrate on the essential design of web applications, abstracting from accidental complexity, such as the details of data persistence. The combination of high-level and low-level constructs ensures high expressivity, while supporting customization to application requirements.