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Re: (more) extensible SAX

• From: Eric van der Vlist <vdv@d...>
• To: xml-dev@l...
• Date: Wed, 06 Dec 2000 02:14:40 +0100

Hi Ken,

Ken MacLeod wrote:
> 
> Eric van der Vlist <vdv@d...> writes:
.../... 
> > While this is certainly an important difference, I don't see it as
> > the main difference, but I'd rather say that the main difference is
> > that SAX and DOM are acting at different levels and that SAX is the
> > most "neutral" interface, DOM being more biased by a specific
> > interpretation of what is a XML document.
> 
> I'll start off by saying I disagree a little with your premise, but
> agree with your conclusion :-)

:-)
 
> SAX and DOM both present the XML InfoSet, one in parse sequence (as a
> stream) and one after parsing is complete (as a tree, and some
> libraries offer a mix of the two).

Yes, but which XML Infoset ? The notion seems very flexible and
different amongst the specifications :) ...

.../...
 
> > What do I mean concretely ?
> >
> > Instead of:
> >
> > startElement(java.lang.String namespaceURI,
> >       java.lang.String localName,
> >       java.lang.String qName,
> >       Attributes atts)
> >       throws SAXException
> >
> > I would have far preferred to have:
> >
> > startElement(org.xml.sax.StartElement start)
> >         throws SAXException
> >
.../... 
> Coincidentally, this is one of the major feature differences with Perl
> SAX[a] (being descussed in the "SAX Comments" thread[b]).  Perl SAX has
> always used a node as the argument to SAX events.  In our case,
> though, it's not a "start element" or "end element" object, but just
> an element node, a DOM node, to be exact.
> 
> For SAX2's namespaces, all that needed adding was Prefix, LocalName,
> and NamespaceURI properties to the nodes.

That's interesting (and proves me that I shouldn't be that Java biased)
especially after the comment from Elliotte Rusty Harold about the added
complexity of such an architecture.

What's your feeling after having implemented and used it ?

> For "raw" parsing, one need only add "raw" information properties,
> like "OriginalStartTag", "OriginalEndTag".  (No one's done that yet,
> but it's on the wish list.)

:)

> Namespace support was such a "simple" change to Perl SAX, that we now
> face the dilemma of changing the class names just because the SAX2
> Java implementation had to change interfaces to support these new
> features.

Yes, I can imagine and that was one of my points.
 
> "Marrying SAX and DOM" was discussed briefly here on xml-dev[c] and on
> Python's XML-SIG[d,e].
> 
> > I don't see anything but advantages, one of them being the
> > extensiblity: with this architecture, SAX2 would just have been a
> > layer on top of SAX1.
> >
> > Have I miss something ?
> 
> Not that I can see, in Perl this has been working splendidly for about
> 18 months.

Thanks.

Eric
 
>  -- Ken
> 
> > [1] http://www.xml.com/pub/a/2000/08/09/xslt/xslt.html
> > [2] http://lists.xml.org/archives/xml-dev/200011/msg00551.html
> 
> [a] <http://bitsko.slc.ut.us/~ken/perl-xml/sax-2.0.html>
> [b] <http://lists.xml.org/archives/xml-dev/200012/msg00047.html>
> [c] <http://lists.xml.org/archives/xml-dev/200003/msg00316.html>
> [d] <http://mail.python.org/pipermail/xml-sig/2000-February/001905.html>
> [e] <http://mail.python.org/pipermail/xml-sig/2000-February/001907.html>
>     follow the thread on "EasySAX"

-- 
See you at XML 2000
      http://gca.org/attend/2000_conferences/XML_2000/building.htm#vlist
------------------------------------------------------------------------
Eric van der Vlist       Dyomedea                    http://dyomedea.com
http://xmlfr.org         http://4xt.org              http://ducotede.com
------------------------------------------------------------------------

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