Fix incompatibilities between Schematron and SVRL

[xatapult]

There are several incompatibilities between Schematron and SVRL. For instance:

• What should be the value of schematron-output/@title. There is nothing in the Schematron spec that fits (not even intuitively)
• The same for active-patter/@name and active-pattern/@role
• In SVRL there is a dir/@role attribute. But not in Schematron
• The same for emph/@class
• Some other problems are the data types of some attributes in the SVRL. For instance assert/@id in Schematron is of (correct) type xs:ID. But in SVRL the corresponding failed-assert/@id is suddenly an xs:NCName

If we're going to keep SVRL we at least must make sure it is compatible with the Schematron language.

[dmj]

See also #7

[rjelliffe]

It is not as simple as just transferring types.

In particular, ID types are supposed to be unique-per-document values. Therefore, if an sch:assert with a @id that is type xs:ID is reported as an svrl:failed-assert with an @id of xs:ID then the SVRL will be invalid everytime the same assertion fails.

This problem will affect every time there are SVRL elements caused by multiple failures, at least: for patterns, rules, asserts, report, property, diagnostic. None of these can have their @id be of type xs:ID. The "id" is not the identifier for the SVRL element, but the identifier of the Schematron element.

So what else can it be? It should not be an xs:IDREF because that implies it is a reference to an ID in the same document.

Therefore the only, and best, XSD Datatype for those is xs:NCNAME.

(And yes I understand that RELAX NG validators may only implement lexical only, and not check uniqueness. But using xs:ID (i.e the datatype defined in XSD with uniqueness semantics) is an assertion that uniqueness should somehow be checked, e.g. by Schematron: it is not saying that there is no uniqueness. )