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RE: Does SAX make sense?

• To: "'Jeff Rafter'" <jeffrafter@d...>,"'Rick Jelliffe'" <ricko@a...>, <xml-dev@l...>
• Subject: RE: Does SAX make sense?
• From: "Martin Soukup" <martin@d...>
• Date: Sun, 25 May 2003 21:40:53 -0400
• Importance: Normal
• In-reply-to: <008e01c3078d$64a47af0$22ecd90c@c1980223a>

> -----Original Message-----
> From: Jeff Rafter [mailto:jeffrafter@d...]
> Sent: April 20, 2003 6:37 PM
> To: Rick Jelliffe; xml-dev@l...
> Subject: Re:  Does SAX make sense?
> 
> > * have the SAX stream kept cached for the lifetime of the document
> > (or have some kind of weak reference perhaps) since they are in
memory
> > anyway (though unreachable), allowing backward-looking XPaths; or
> 
> XPath comes up here and came up in several of the other responses.
Perhaps
> someone could answer what class of XPaths, if known prior to document
> parse,
> can not be satisfied during the document parsing?
> 
> <root>
>   <child name="C1">Foo</child>
>   <child name="C2">Bar</child>
> </root>
> 
> If, before parsing, we know that we need to satisfy
> "/root/child[@name='C2']" Why could this not be satisfied? Maybe
coming up
> with a common SAX->XPath->Results Filter which had a standard
mechanism
> (e.g. Interface?) for passing back XPath results as encountered in the
> process of a SAX stream would be a good plan.
> 
> It strikes me that even the preceding-sibling and ancestor axes could
be
> handled with a simple stack. This would still limit memory consumption
and
> the objects in the stack could be reused for different "branches".

This simple stack mechanism is how I implemented this. Of course you
have to protect against DoS attacks through user input infinite
recursive expressions.

> If all of this was embedded in an interface so that you could register
> XPaths before the document parse, and then receive callbacks (or
store)
> the
> results of those XPaths you would have something pretty nice. Does
this
> already exist?

There are several implementations, but I don't know of any standard
interface. I have been thinking that having a standard interface just
for passing XPath expressions to an event parser would be great. Anyone
know of a standard being worked, implementations, or interested in
starting a working group? If so, I'm in.

Martin.

> Cheers,
> Jeff Rafter
> 
> 
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