How do you design an extensible domain-specific language?

2 Choose your syntax

The next step is to choose the syntax of your DSL, which is the set of rules and symbols that define how your DSL is written and read. You have two main options: external or internal syntax. External syntax means that your DSL is independent of any host language, such as Java or Python. You need to create your own parser and interpreter or compiler for your DSL. Internal syntax means that your DSL is embedded within a host language, using its features and tools. You need to follow the host language's syntax and semantics. Both options have pros and cons, depending on your domain, target audience, and implementation goals.

4 Test your DSL

The fourth step is to test your DSL, which is the process of verifying and validating that your DSL works as intended and meets the domain requirements. You need to test both the syntax and the semantics of your DSL, using different methods and tools. For example, you can use unit testing, integration testing, or acceptance testing to check the correctness and performance of your DSL code. You can also use static analysis, dynamic analysis, or debugging tools to detect and fix errors or bugs in your DSL code. You should also involve your domain stakeholders in testing your DSL, by collecting their feedback and suggestions.

5 Document your DSL

The fifth step is to document your DSL, which is the process of creating and maintaining the information and instructions that explain how to use and extend your DSL. You need to document both the syntax and the semantics of your DSL, using different formats and media. For example, you can use formal specifications, informal descriptions, or examples to illustrate the rules and features of your DSL. You can also use tutorials, guides, or reference manuals to teach and support the users and developers of your DSL. You should also document the design and implementation decisions and trade-offs that you made for your DSL.

6 Evolve your DSL

The final step is to evolve your DSL, which is the process of updating and improving your DSL according to the changing needs and expectations of your domain. You need to monitor and evaluate the usage and impact of your DSL, using different metrics and indicators. For example, you can use code analysis, user feedback, or domain analysis to measure the quality, usability, and relevance of your DSL. You can also use version control, refactoring, or migration tools to manage the changes and enhancements of your DSL. You should also communicate and collaborate with your domain stakeholders in evolving your DSL, by soliciting their input and participation.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?