HashML Schema Schema
HashML schemas are themselves written in HashML. Seeing that a schema file is simply a HashML document, we can write a schema for schema files. We call this the schema schema: it's a schema for defining schemas.
The schema schema defines the HashML Schema Language, an application of HashML. It defines the HashML tags that can be used to define a schema, and some rules on how these tags should be used.
The schema schema is self-referential: it describes the schema language, and is itself a valid schema. This means that the schema schema can always be parsed with itself.