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Comment about 2.2.2 The luhn() Function (XForms 1.1)

From: David Landwehr <david.landwehr@solidapp.com>
Date: Tue, 07 Mar 2006 21:39:07 +0100
Message-ID: <440DEF6B.1010301@solidapp.com>
To: www-forms@w3.org, www-forms-editor@w3.org

Dear Working Group,

I noticed that one of the examples for the luhn function was expressed 
as luhn(.). I guess this is made explicit as an example since this is 
the most common use case. E.g. constraint="luhn(.)". Why not leave the 
argument for the function optional and say that in case it is laking 
then the context node are used (as XPath does for local-name(), 
string-length() and others).

This would leave the definition to something like:
/boolean/ *luhn*(string?)

If the string parameter conforms to the pattern restriction of the 
xforms:ID-card-number <http://www.w3.org/TR/xforms11/#id-card-type> 
type, then this function applies the |luhn| formula described in [ISO 
7812-1:2000] <http://www.w3.org/TR/xforms11/#ref-iso-7812> and returns 
true if the number satisfies the formula. Otherwise, false is returned. 
If the string argument is omitted it defaults to the context node 
converted to a string.

It would really help implementors if there was at least one example 
showing an argument where luhn return true.

Editorial: XPath and XSLT uses the term argument for arguments where 
XForms seems to call them parameters (not in all function definitions 
but in most of them).

Best regards,

David Landwehr (david.landwehr@solidapp.com)
Chief Executive Officer, SolidApp
Web: http://www.solidapp.com
Office: +45 48268212
Mobile: +45 24275518
Received on Tuesday, 7 March 2006 20:39:11 UTC

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