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Re: L3 LS: Configuration parameter to enable/disable application specific DOM

From: Steve Schafer <steve@fenestra.com>
Date: Sat, 03 Jan 2004 20:08:39 -0500
To: www-dom@w3.org
Message-ID: <gllevvog3us87uu2gvlu6ja8dlltkj6sfv@4ax.com>

On Sat, 03 Jan 2004 17:26:03 -0600, Curt Arnold <carnold@houston.rr.com>

>I'd like comments on this if anyone has thought this through.  Assume 
>that you have an implementation that supports Core on generic XML 
>documents and application specific DOM, such as L2 HTML, SVG or MathML.  
>If you automatically created the application specific elements when you 
>encounted recognized elements, you may incur additional overhead in DOM 
>building and may reject documents that are valid XML but aren't valid 
>XHTML or SVG.  However, if you don't automatically do that, you always 
>get a generic DOM implementation.  I think that doing this right would 
>require an additional configuration parameter in LSParser, but I haven't 
>thought through what that would look like.

I'm not sure I understand what you're asking, but let me see if this is

You want a configuration switch that tells the parser to behave as an
"application-aware" parser vs. a generic parser. If set to
"application-aware," and it encounters an invalid element or attribute,
it would presumably fail in some way, or attempt some kind of recovery,
etc. If set to "generic," it would succeed as long as the document is
well-formed (you said "valid" in your message, but I think you meant
"well-formed," no?), but the downside is that the final result is a
generic DOM object tree, devoid of any language-specific semantics or

Is that a reasonable elaboration?

In my own work, I've put together a system that instantiates elements
and attributes on a purely namespace+scoping basis. "Smart" elements are
instantiated based on their qualified names, and "smart" attributes are
instantiated based on the combination of their qualified names plus the
qualified names of the elements that own them (this is necessary for
SVG, where the same name is used for attributes having different
semantics when contained within different elements).

If a qualified name is not recognized by the parser, it "falls through"
and a generic DOM element or attribute object is instantiated. So, in a
limited sense at least, the parse always succeeds, in that the parser
never fails because of invalidity. However, it's possible that an
attempt to insert the wrong kind of content or attribute into an element
might cause an exception to be raised. For example, assuming my parser
understands both SVG and XHTML:

 <!--namespace declarations omitted for brevity-->

Here, the <html> element will be instantiated successfully, but an
exception will be raised upon the attempt to insert it as a child of the
<svg> element. Note that the exception is not raised by the parser, but
by the "smart" <svg> element itself, which knows that it shouldn't have
an <html> element as a child.

Anyway, back to your question: I'm not sure that I would consider this
to be as much a parser configuration setting as an application
configuration setting. At least part of my rationale for this is because
of the way my parser works, as described above--it's left up to the
"smart" elements themselves, rather than the parser, to decide what's
right and what's not.

Steve Schafer
Fenestra Technologies Corp
Received on Saturday, 3 January 2004 20:09:39 UTC

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