still stuck on requirements

From: David R. Karger <karger_at_mit.edu>
Date: Fri, 20 May 2005 01:26:55 -0400

I'm slowly catching up on this mailing list, and am seeing the
discussion beginning to move towards specific questions of the lens
and style vocabulary. I'm still stuck on some more basic questions.

Chris uses the terms "selection" and "styling", but also argues for a
device-independent notion of style. Let me take those terms
literally, as sating that a set of lenses tells us _only_ what logical
information needs to be conveyed to the user---ie, what properies and
values. It is really just selecting a subset of the rdf. It says
nothing about the way those properties and values should be presented.
The "output" of a lens might just as well be an rdf graph, since that
is as good a way as any of representing that logical information.
Styles are the first time that any thought arises about how that blob
of selected statements should be presented to the user. It is then
fair to ask, is there anything device independent about such
presentation decisions? Arguably yes: we might want to make
assertions about which resources or relations in the selected model
are "central" and which are "peripheral".

But the lens example below does not only select information to show;
it also indicates structure-of-presentation, at least implicitly---ie,
does lens below (taken from chris' email) demand implicitly that all
the people this person knows should be shown together? Or is it a
pure selection, that just says we should includes all the :knows
statements in the selected submodel, but that a device might choose to
display those knows relations in arbitrary ways?

:personsKnowsLens rdf:type fresnel:Lens ;
fresnel:lensDomain foaf:Person ;
fresnel:showProperties ( foaf:firstname
                        foaf:mbox
                        foaf:depiction
                              [ rdf:type fresnel:PropertyDetails ;
                                fresnel:property foaf:knows ;
                                fresnel:sublens :FriendLens ] ) .


I guess another possible lens behavior might be to materialize a
property that is not explicit in the data model. For example, one
could a imagine a lens deriving "grandchildren" of a person by
squaring the child relation, and shipping an rdf model containing
grandchild assertions, even though the original data model contains no
grandchild property. Or, should we require that the lens _only_
filters and does not create new statements?
Received on Fri May 20 2005 - 05:25:27 EDT