> For the complete documentation index, see [llms.txt](https://docs.rainbird.ai/rainbird/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rainbird.ai/rainbird/knowledge-modelling/modelling-features/rblang-reference.md).

# RBlang reference

RBlang is Rainbird's XML knowledge representation language. Studio and Co-author generate it. You can inspect and edit it in the code panel when you need low-level control.

Use this section when you:

* need precise syntax
* need to fix low-level validation errors
* want an LLM to generate valid RBlang

### Start with these rules

1. Only `string` concepts can be relationship subjects.
2. Use the `value` attribute for assignment. Never use `=` for assignment.
3. Do not create concept instances for `number`, `date`, or `truth` concepts.
4. Use single quotes for string literals in expressions.
5. Keep relationship names unique across the whole knowledge map.
6. Test missing facts with `countRelationshipInstances(..., 'relationship name', *) is equal to 0`.

### In this section

* [XML structure and namespaces](/rainbird/knowledge-modelling/modelling-features/rblang-reference/xml-structure-and-namespaces.md)
* [Concepts, relationships, and instances](/rainbird/knowledge-modelling/modelling-features/rblang-reference/concepts-relationships-and-instances.md)
* [Rules and expressions](/rainbird/knowledge-modelling/modelling-features/rblang-reference/rules-and-expressions.md)
* [Functions reference](/rainbird/knowledge-modelling/modelling-features/rblang-reference/functions-reference.md)
* [Validation checklist and examples](/rainbird/knowledge-modelling/modelling-features/rblang-reference/validation-checklist-and-examples.md)


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