Just to check that by "valid potential QName" you mean a string that is in
the lexical space of xs:QName and will therefore constitute a valid QName
provided the prefix is in scope?

($x castable as xs:QName) will not work because (a) it also tests whether
the prefix is in scope, and (b) to avoid the issues of it therefore being
context-sensitive, the W3C spec says this is only allowed if the argument
($x) is a string literal.

So you do need to use the regex approach.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay   

> -----Original Message-----
> From: ac [mailto:ac@xxxxxxxxxxxxx] 
> Sent: 03 February 2010 07:30
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject:  are all strings in a sequence valid potential QNames
> 
> Hi List,
> 
> As for example, in determining element and/or attribute names 
> from the first line of a csv file, as well as other similar 
> cases, with xslt2.0 (e.g. without "map", "try", and schema), 
> what is the best way to check (e.g. true/false) that 1. a 
> string is a valid potential QName (e.g. match + what regex?, 
> or other option) 2. all strings in a sequence are valid 
> potential QNames
> 
> Thank you,
> ac