> features that it has is the ability to subclass ElementNode with custom > Elements. In conjunction with an ElementFactory that allows creating custom > This is great, and if Xerces does it, that's fine. Still, it means that your code is tied to a particular implementation.
Even if the DOM you use allows any Element implementors in the document, no DOM is required to support this, so the code would still not be portable. It seems that DOM Level 2 is trying to address this (and related issues) with the "importNode" method being put on the Document interface. I have not studied the spec enough to know whether an implementation would be allowed to just return the original pointer in case it was already compatible. - Tom Palmer
