Wednesday, June 9, 2010

MSXML.createNode method (docs,design,standards?)
A string defining the namespace URI. If specified, the node is created in the context of
the namespaceURI parameter with the prefix specified on the node name.
If the name parameter does not have a prefix, this is treated as the default namespace.

The marked part may be a bit problematic to interpret.
In the reality it means that createNode will create unprefixed element or attribute and
produce xmlns="ns" declaration.

This is fine for elements because of xmlns scoping.
However this leads to troubles if creating
unprefixed-namespaced-attribute on unprefixed-namespaced-element with different namespace,
and also if creating
prefixed-namespaced-attribute on prefixed-namespaced-element with different namespace and same prefixes.
var root = d.createNode(1, "root", "nsRoot"),
    ch1 = d.createNode(1, "p:child", "nsChild"),
    ch2 = d.createNode(1, "child", "nsChild"),
    a1 = d.createNode(2, "p2:a1", "nsAttr"),
    a2 = d.createNode(2, "a2", "nsAttr");

The last line will fail, with "bit problematic to interpret" error,
showing authors misinterpretation of namespace and prefixe terms ;-)

There was a Namespace conflict for the '' Namespace.

Actualy there was a conflict for '' prefix between nsChild and nsAttr namespaces.

XML without last line will look like this:
<root xmlns="nsRoot">
    <p:child xmlns:p="nsChild"/>
    <child xmlns="nsChild" xmlns:p2="nsAttr" p2:a1=""/>

Try to rewrite this code with createElementNS and createAttributeNS in different browsers.
Some are able to autogenerate prefixes if already taken by another namespace, some produce funny results.

MS is lucky not to declare compliance, however the docs are confusing and
prefix colisions unsolved.

Another silly decision is that namespaceURI does not accept null.
The closes standardized method (DOM2 Level createElementNS) speaks abou null values, and all browsers implement
both null and "" as "unqualified".

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