[DDI-SRG] Two further URN/ID issues

[Joachim Wackerow]

URNType in reusable should be formally described by a regular 
expression. This way basic syntax check for URN's is possible by 
validating against the XML Schemas. Currently URNType is just xs:anyURI, 
which seems to be very lax.
Are there any reasons, why regular expression are not used already?


BaseIDType is a xs:string restricted by the regular expression 
([A-Z]|[a-z]|\*|@|[0-9]|_|$|\-)*
The field documentation says: Valid characters include A-Z, a-z, @, 0-9, 
_, -, $

There are two issues with this:
- the dollar sign should be escaped in the regular expression
- the asterisk - mentioned in the regexp is not described in the 
documentation

Anyway, I'm wondering why are special signs ("*", "$", "@") necessary in 
an id. Are they really required?

Especially the "@" can make problems in DDI URN resolution services. 
Some resolution service will use a REST-based approach for querying 
URN's like:
http://xy.org/DDIURNResolutionService?URN

URN is the query string of this URL. It stands for the complete DDI URN. 
A "@" is not allowed in a query string. It must be escaped according the 
rules for URL's. This is surely be possible, but makes things more 
complicated.
Does "@" make really sense in an DDI ID?

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