XFA Specification
Chapter 15, Template Specification
Template Reference
541
The usehref property
Invokes an external object as a prototype for this object. The content of this property is an URL, followed
by '#', followed by either an XML ID or by som(SOM_expr) where
SOM_expr
represents a SOM expression.
The XML ID or SOM expression is resolved in the context of the external document.
If both
use
and
usehref
are non-empty
usehref
takes precedence.