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Re: Validate an XPath with regex

• To: Niels Peter Strandberg <nielspeter@n...>
• Subject: Re: Validate an XPath with regex
• From: Francis Norton <francis@r...>
• Date: Thu, 04 Apr 2002 13:04:42 +0100
• Cc: xml-dev@l...
• References: <3B1C9D22-47A6-11D6-8473-000502CB905D@n...>
• User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.9) Gecko/20020311

Hi Niels,

I'm not a linguistics expert but I think that regular expressions and 
XPath expressions come at different levels of the Chomsky hierarchy [1] 
- regular expressions would be type 3, Regular, but XPath would be type 
2, Context Free. One notable difference is that you can't specify 
balanced syntax with type 3 grammars, so you couldn't specify anything 
requiring correctly nested square or round brackets for instance.

Hope this helps -

Francis.

[1] http://www.wikipedia.com/wiki/Chomsky_hierarchy

Niels Peter Strandberg wrote:

> Shouldn't it be possible to validate the syntax of an XPath string 
> using regular expressions. Im not a regex expert, so just want to ask 
> you out there if it could be done.

• References:
  • Validate an XPath with regex
    • From: Niels Peter Strandberg <nielspeter@n...>

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