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- From: Mark Birbeck <Mark.Birbeck@iedigital.net>
- To: 'Paul Prescod' <firstname.lastname@example.org>, 'XML Dev' <email@example.com>
- Date: Mon, 12 Apr 1999 21:14:53 +0100
> Excelon implements a DOM interface to XML documents, not to
> arbitrary data objects. That doesn't make it a bad product,
> but I don't think it is the product Mark is describing. I imagine that
> the (imaginary) product that Mark is describing would allow you
> to specify your objects in IDL, manipulate them as ordinary
> object/method/property Java or C++ objects and get a DOM interface
> to them "for free" when you want it. I don't think that that product
That's true, Paul, thanks.
I was also imagining that:
- when I want the last node from a tree that contains 100,000 nodes
that the whole 'document' would not be read into memory.
- that I could access the tree as if it was a complete DOM with
all the caching and so on being done for me.
- that if I perform an XSL-type query I will get the nodes I want,
regardless of whether they are in memory or not.
I have implemented a very crude version of this. I use the IE5 DOM and
with this I retrieve documents from our database using URLs that are a
scaled down version of XQL (I can't say I like XPointer). For example:
would retrieve all 'article' objects with an author attribute of 'Mark',
that are children of a node of type 'documents'. This would then be
returned to the caller as an XML document, but with a stylesheet PI
pointing to 'stylesheets/article.xsl'. (Replacing .xml with .htm would
yield the same results but the XML and XSL would be combined for you on
The problem with this is that I have to convert this request to a query
on the objects in the hierarchical database in order to populate my DOM.
Of course, once in the DOM I can export it as XML or transform it if
necessary, so the database does look from the outside like it is one
great big XML document.
But although I am quite happy with this so far, I can see that you would
have to code this up for every type of database, and really it should be
a job for the DOM. It really needs a layer like the layer above the
database-specific layers in ODBC; it would sit just below the DOM. This
layer would obviously need to understand schemas, so it wouldn't be a
trivial task to implement.
Anyway, my original question was 'is anyone doing anything like this?'
and I think the answer is 'nowhere near yet!'
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