In this presentation recoded during QCon London 2008, Magnus Christerson discusses about the importance of using DSLs which allow business experts to freely express their knowledge about their domain using familiar tools. Henk Kolk presents a concrete example addressing pension fund issues and based on a DSL.
Watch: Domain Expert DSLs (1h)
In the first part of the session Christerson talks about Intentional Software Development emphasizing the need for domain experts to be able to freely express their knowledge of the domain and intentions for the product to be created by using the tools they are accustomed with. The domain experts are practically using a DSL to write the specifications. Since such specifications are not directly executable by a computer, the programmer’s job is to create a code generator translating the specs into code (Java, C#, Ruby, etc.). The result is a clear separation of concerns between business experts and programmers. The former are responsible for clearly and correctly expressing the business rules of the domain, while the later are concerned only with the automatic translation of the document written in the specified DSL into code. They work together on the language workbench which Martin Fowler defined as follows:
1. Users can freely define new domains, including languages, that are fully integrated with each other.
2. The primary source of information is a persistent abstract representation.
3. Domain designers define domains in three main parts: schemas, editors, and generators.
4. Domain users manipulate a domain through a projectional editor.
5. A domain workbench can work with incomplete and contradictory information.
In the second part of the session Kolk talks about a concrete Capgemini project that uses a DSL to create a solution for pension funds. Their program accepts business rules that pension domain experts are used with and converts them into Java or C# code.
The session concludes with Christerson and Kolk answering questions.