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> -----Original Message----- > From: Ronald Bourret [mailto:rpbourret@r...] > Sent: Thursday, November 15, 2001 5:00 PM > To: xml-dev@l... > Subject: Re: Interoperability [long] > . I process DOM trees (which do use multiple namespaces) in a > similar manner. > > What am I missing here? The gotchas in DOM/namespace processing, as I recall from about three years of DOM WG meetings wrestling with this wretched subject are (my psychological defenses have probably erased some of the more painful memories, so help me out here ...): - The DOM WG naively believed a literal reading of the namespace spec and treats prefixes as mere syntax sugar and URIs as the "real thing". This causes problems when interoperating with specs that treat prefixes as being significant. - Elements created with a namespace URI may not have a prefix, and you may have to invent one when you need one, e.g., when serializing. - The DOM lets you create elements with an invalid namespace URI, partly because the very notion of "invalid namespace URI" is not well defined, and partly because requiring continual checks against all the numerous well-formedness constraints (no "--" in, comments, no illegal Unicode code combinations in content, etc) would require DOM implementations to be very slow; the decision was made to perform these checks at normalization or serialization time). Anyway, you can create an element in a NULL NS URI, and that is not NS-well-formed. - since DOM nodes don't intrinsically know their namespace (unlike XPath nodes, as I understand it), the namespace of a node when moved around in the tree may change in undesireable ways unless you take lots of care to make sure that it is in the same namespace scope in the source and target locations, or that you *intended* to make that HTML <p> element a <p> element in the "foo" namespace .... - Mixing nodes created with Level 1 namespace-blissfully-ignorant methods and Level 2 namespace-aware methods can lead to undefined and non-interoperable scenarios. The DOM Level 2 spec says, translated into suitable W3C-ese, "there be dragons, abandon all hope ye who venture there." Basically, the namespace spec provides a lot of handy rigging in a read-only environment, but you'll find that you have more than enough rope to hang yourself once you start creating elements in non-declared namespaces or moving elements between namespaces with the DOM. St. George himself couldn't rescue you if you muck around with namespaces and entities simultaneously ...
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