The URIReference interface

[1]

A <IF::URIReference> object represents a DOM URI.

    A <IF::URIReference> object <kwd:MAY> also implement
    scheme-specific interfaces.

      {NOTE::
        Modifications to the object, via the <A::URIReference.uriScheme>
        attribute for example, might or might not result in
        mutations of the interfaces implemented by the object,
        since dynamic rebinding of classes might not be supported
        in the programming language or the DOM binding in use.

 If a method or attribute that is inappropriate for
        the underlying DOM URI represented by the <IF::URIReference>
        object is invoked, the result is undefined, unless
        the specification of the interface defines any error
        handling behavior.  However, implementators are advised
        to make the method or attribute implementations torelant
        and harmless as far as possible.