[sc34wg3] Some inconsistencies in the tmcl schema

Lars Marius Garshol larsga at garshol.priv.no
Wed Oct 28 07:31:07 EDT 2009

* Michael Quaas
> But the datatype regexp still exist as it is used as an occurrence- 
> type
> for the subject-{identifier/locator}-constraint. Or do you propose to
> remove the datatype regexp in general and just use xsd:string instead?

We currently have tmcl:regexp. This is an occurrence type. (Not a  
datatype). The TMCL schema gives its datatype as xsd:string.

The occurrence type is of course going to stay in TMCL, because we  
need it, for exactly the reasons you give. I understood your question  
to be whether we should create a datatype for regular expressions, and  
explained why I thought we shouldn't do this.

> But even so the regular expression for the re-ex-co must be stored
> somewhere, isn't it?

You mean, the regular expression that the values of tmcl:regexp  
occurrences must follow? There is no such expression, I'm afraid. The  
XML Schema regular expression language is not a regular language. In  
other words, you cannot express its syntax with a regular expression.  
You have to use a context-free grammar for this.

So the way we ensure that tmcl:regexp only contains valid regular  
expressions is by saying in the text that it must. I now notice that  
we don't do this, so clearly that's another edit required in the  
spec. :-)

--Lars M.

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