The title of Rule 11-49 uses "document" in the title after the first schema reference, not after the second. The title of Rule 11-48 does not use "document" at all. Suggest using consistently or removing.
Rule titles may not be immediately obvious. The schematron error messages provide enough clarification, but it would be more reader friendly to either copy that message below the rule title so the schematron does not have to be read, or to reword the rule titles a bit. Something like...
Conformant import in a reference schema must be a reference schema
Conformant import in an extension schema must be a reference or an extension schema
Something that doesn't raise questions about what happened to externals, or if certain imports are required.
I think it's OK that the rule title doesn't have all the details for the rules; that would be a high bar that other rules don't meet. Revised rule title for consistency (e.g., "reference schema document").
11.8. Schema assembly
Rule 11-48. Reference schema imports reference schema Rule 11-49. Extension schema document imports reference or extension schema
The title of Rule 11-49 uses "document" in the title after the first schema reference, not after the second. The title of Rule 11-48 does not use "document" at all. Suggest using consistently or removing.
Rule titles may not be immediately obvious. The schematron error messages provide enough clarification, but it would be more reader friendly to either copy that message below the rule title so the schematron does not have to be read, or to reword the rule titles a bit. Something like...
Conformant import in a reference schema must be a reference schema Conformant import in an extension schema must be a reference or an extension schema
Something that doesn't raise questions about what happened to externals, or if certain imports are required.