Using XML namespaces

Question

While searching Web I encountered many examples of using namespaces in XML files. They mostly have this form:

<d:student xmlns:d='http://www.develop.com/student'>
  <d:id>3235329</d:id>
  <d:name>Jeff Smith</d:name>
  <d:language>C#</d:language>
  <d:rating>9.5</d:rating>
</d:student>

(this is example taken from https://msdn.microsoft.com/en-us/magazine/cc302166.aspx)

This line:

<d:student xmlns:d='http://www.develop.com/student'>

troubles me, pretty much because every example looks like this. Can it have a form of

<student xmlns:d='http://www.develop.com/student'>

So here I am declaring the same namespace identified by the same URI, but i don't want node where declaration is to have namespace. Is it correct? Long story short: is just xmlns:d='http://www.develop.com/student' a valid declaration for d: namespace?

Quentin · Accepted Answer · 2015-01-21 10:50:30Z

1

xmlns:d='http://www.develop.com/student' will declare the d namespace for that elements and all its descendants.

It will not make the element come from that namespace if it lacks d: on the tag name. That will still use the default namespace.

i.e.

<foo xmlns="http://example.com/1">
    <bar xmlns:x="http://example.com/2">
        <x:baz />
    </bar>
</foo>

foo comes from /1. bar comes from /1. baz comes from /2.

answered Jan 21, 2015 at 10:50

Quentin

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ThW · Accepted Answer · 2015-01-21 13:14:09Z

d ist not the namespace but an alias for it (that is usable as a prefix). The namespace is still http://www.develop.com/student.

<d:student xmlns:d='http://www.develop.com/student'/> can be read as {http://www.develop.com/student}:student.

It is possible to define a default namespace for elements without a prefix using the xmlns attribute. So <student xmlns='http://www.develop.com/student'/> can be read as {http://www.develop.com/student}:student, too.

The DOM keeps the namespace and the localname in separate properties of the node objects actually. The {namespace}:localname syntax is often used for debug outputs.

A namspace deifnition is always valid for the element node it is defined on and all its descendants (unless it is overwritten in a descendant).

Attribute nodes do not use the default namespace definition. Attributes without a prefix are always in the "empty" namespace.

Here is an example that doesn't use prefixes.

<student xmlns="http://www.develop.com/student">
  <id>3235329</id>
  <name>Jeff Smith</name>
  <description type="xhtml">
    <div xmlns="http://www.w3.org/1999/xhtml/">
      ...
    </div>
  </description>
</student>

The node names in the example (with resolved namespaces) are:

{http://www.develop.com/student}:student
{http://www.develop.com/student}:id
{http://www.develop.com/student}:name
{}:type
{http://www.w3.org/1999/xhtml/}:div

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