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Confusion while implementing the DOM.

• From: Andrew Douglas <andrew.douglas@n...>
• To: xml-dev@i...
• Date: Wed, 2 Jun 1999 12:09:10 +0100 (BST)

Hi,

I've been given the job of implementing a web-content management tool.
We (I) have decided that valid XML documents are, at the moment, the
best way to go.  So I've been building my own classes for implementing
XML and DTDs, and have added the DOM as one of the features I want to
support.

Now, I know the DOM is independent of the implementation of XML documents,
but my question is, how closely can I reveal my implementation through
the DOM?  Consider a simple DTD:

  <!Element root (elone, eltwo)*>
  <!Element elone (#PCData)>
  <!Element eltwo (#PCData)>

A simple document meeting this would look as so:

  <root>
    <elone>Hello</elone>
    <eltwo>Goodbye</eltwo>
    <elone>Gutten Adbend</elone>
    <eltwo>Aufwiedersehen</eltwo>
  </root>

My underlying structure looks like this


                         opentag(root)
                            |
                        zomcontent
                |-----------+-----------------|
            sequence                      sequence
         |------+-----|                |------+-------|       
 opentag(elone) opentag(eltwo) opentag(elone) opentag(eltwo)
       |               |              |             |   
     text            text           text          text
     
Not suprisingly, it looks like a tree!  So, all these things can be
Nodes, but not all are Elements (opentags are) -- some are
probably DocumentFragments(zomcontent, sequence, ...).

So, my DOM implementation has the usual first/last Child, getChildNodes,
get Next/Previous siblings, and so on, but sometimes these children aren't
Elements, but are DocumentFragements.

Also, taking the above tree as an example, each opentag(elone) has a single
NextSibling, but no PreviousSibling (and vice versa for opentag(eltwo)s).
Please can someone tell me if this acceptable?  The books/Spec don't really
say that much about it all.

Thanks,
A.

PS The only one I've probably implemented correctly is getNodesByTagName,
which returns a NodeList guaranteed to contain only Elements.


---------------------------------------------------------------------
Andrew Douglas,               andrew.douglas@n...
Netcentric, Unit 3, Copley Hill Farm,Cambridge Road,Cambridge,CB2 4AF
http://dougie1111.ecode.com/ ;-)


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