Declaring Namespaces

The XML parser provides support for associating elements and attributes with namespaces. There are two ways of declaring namespaces: default declaration and explicit declaration.

Default Declaration

The default declaration declares a namespace for all elements within scope.

<BOOK xmlns="urn:BookLovers.org:BookInfo"> 
  <TITLE></TITLE>
</BOOK>

The following example declares the "BOOK" element and all elements and attributes within it ("TITLE", "PRICE", "currency") are from the namespace "urn:BookLovers.org:BookInfo". The attribute "xmlns" is an XML keyword and is understood by the parser to be a namespace declaration.

<BOOK xmlns="urn:BookLovers.org:BookInfo">
  <TITLE>A Suitable Boy</TITLE>
  <PRICE currency="US Dollar">22.95</PRICE>
</BOOK>

Default declarations are useful when a node (element and subelements) is from the same namespace.

Explicit Declaration

The following example declares "bk" and "money" to be shorthand for the full names of their respective namespaces. All elements beginning with "bk:" or "money:" are considered to be from the namespace "urn:BookLovers.org:BookInfo" or "urn:Finance:Money," respectively.

<bk:BOOK xmlns:bk="urn:BookLovers.org:BookInfo"
         xmlns:money="urn:Finance:Money">
  <bk:TITLE>A Suitable Boy</bk:TITLE>
  <money:PRICE money:currency="US Dollar">22.95</money:PRICE>
</bk:BOOK>

Explicit declarations are useful when a node contains elements from different namespaces.