XPointer processor's input

The XPointer framework spec says that an XPointer processor takes as
input just two things: an XML resource and a putative pointer. However,
the xpointer() scheme requires more input, namely the nodes (if any) to
be returned by the here() and origin() functions. So perhaps there
should be a sentence along these lines:
    Individual scheme specifications may require the application to
    pass additional information to the XPointer processor.

-Michael Dyck