Vocabularies and validation

[karinbredenberg]

• We have made our own attributes in our own extension schema to METS. When there are a value list coming from our vocabulary the value is in a enumeration in the attribute schema.
• When we have added a value list to a element/attribute in METS we don't add the value in a value list thus not changing the METS schema.
• The own attributes that can be added and we add dont get validated through the METS-schema, the validation type is LAX so Schematron rules need to be created for this.
• The value lists for METS attributes/elements that we have created needs to have Schematron validation.

This validation part needs to be available to all using the specification regardless of using the validation tool or not.

@carlwilson add all assignee needed for this issue. And split the issue if needed.

[karinbredenberg]

How to do own extensions and so on needs to go into a guideline.