Extension attributes (XSLT only)
An extension attribute is an extra attribute on an XSLT-defined element. These attributes are all in
the Saxon namespace http://saxon.sf.net/. This namespace needs to be declared in a namespace declaration,
but it does not need to be listed in the extension-element-prefixes attribute.
For example, the saxon:assignable attribute can be set as follows:
The extension attributes provided with the Saxon product are as follows: