JSON Schema or Langium

[paulfrench]

If I'm happy with the JSON syntax and happy to specify a JSON schema to enforce data entry what advantages would I get from using Langium ?? There is plenty of editors to create JSON data based on JSON schema. I could code generate from this JSON data.

What extra power would Langium give me apart from creating your own specific DSL ?

I'm being asked some questions and now I'm not so sure.

Cheers

[msujew]

Hi @paulfrench,

If you're happy with an existing language, there's actually little need for Langium or any other language workbench for that matter. While Langium offers a bit more granularity and feature support (such as cross references), being able to reuse existing tooling for a language is usually preferred.

In the same vein, you probably wouldn't try to reimplement JavaScript in Langium, but use an existing JavaScript parser/editor instead, wouldn't you? @spoenemann Your opinion on that?

[paulfrench]

Thanks @msujew, what I mean is if I have a need to create some form of grammar/specification for a specific domain area from which I will code generate for, unless my grammar is fairly complex am I not better to use JSON and JSON schema (or for argument sake xml and xml schema)? Visual tooling for JSON or XML editing with schema enforcement are common, and with a little meta-data, can be made to look very nice using icons etc. JSON schema via $data does allow the enforcement of cross references to actual data entered, I believe it is limited to certain parts of the JSON schema though.

So it was just your thoughts really? I'm starting to think JSON and JSON schema is a good candidate to code gen from for fairly simplistic definitions and maybe Langium for more complex specifications(grammar).

I have a requirement coming down the road where a web visual build tool to create these specifications is required and so not sure what to do. I really like Langium but I believe it has the ability to display a specification based on a grammar visually but there is no plans to allow building visually.

I appreciate your thoughts?

[msujew]

I see, that's what you mean. If your data is purely structural, key-value pair based, there's no real use case for Langium.

Langium for more complex specifications

Right, as soon as your language becomes less config/pure data and more behavior oriented (i.e. mathematical expressions, functional programming, logic programming, OOP), JSON/XML stop being an option usually, and you need something more powerful. That's what Langium is for. Someone from Itemis (the developers of Xtext) has a great blog post on that topic.

I really like Langium but I believe it has the ability to display a specification based on a grammar visually but there is no plans to allow building visually.

Yeah, you can display your AST using the langium-sprotty package. We had some thoughts about supporting the GLSP specification which would also allow for visual editing, but so far no concrete plans for that.

[spoenemann]

If you're happy with key-value mappings and arrays, JSON is perfect. There are several reasons to use a DSL (and thus Langium) instead, here are a few that come to my mind:

• Include behavior (expressions, functions, statements etc.) instead of just structural data
• Shorter syntax and better readability (no need to enclose every name in quotes), especially for non-technical users
• Advanced editor features like custom live validation checks