[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Regular Expressions in XPath 2.0
On 4/23/07, Michael Kay <mike@xxxxxxxxxxxx> wrote:
> I thought I'll share the above presentation as regular > expressions in XPath are based on Perl. Good point, thank you for clarifying.
Ok. There are some interesting trade-offs between the time taken to compile a regular expression and the time taken to execute it. Determinizing an NFA can be an expensive operation. This is rarely discussed in the theory, as far as I can tell, though some of the papers do talk about incremental determinization. You see this in schema processors (which use the regular expression approach to validate an XML document against a grammar) - Saxon creates a deterministic FSA for this, which has excellent run-time performance, but in pathological cases creating the DFSA can be extremely slow.
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