When you import schemata, you may specify a 'schemaLocation' attribute.
This isn't always the same when you distribute schemata:
My recommendations:
Use a 'schemaLocation' attribute when you are distributing the imported schema documents.
Don't specify a 'schemaLocation' attribute when you aren't distributing them. Instead:
Use a catalog to locate the imported schema.
Document the need for the imported schema document and recommend solutions.