Ella,
There are several reasons the main one being that it allows for a
better integration within the Meta-directory service we are trying to
construct. I am sorry to say that things are so busy now just before
the IETF that I don't have the time to go into detail on this in this
audience. If you are curious for more on this topic I suggest you send
you queries to wps(_at_)SURFnet(_dot_)nl, where the meta service is being
discussed. Someone else will surely take time to answer you.
You should also try to join us for the BOF on WPS in Seattle (monday).
Erik