I was going to point out that the fairly popular FoaF (”Friend of a friend”) vocabulary captures friendship, but they settled for foaf:knows because they want it to be “intrinsically vague” :-) , and pushed friendOf, antagonistOf, ambivalentOf, etc. into a separate relationship model.

If you’re looking for proposals, I think just do the search against all parts of the triple in all namespaces. (CPUs are fast :-) ) Then print the matching triples as “Sasha hasFriend Morrel” , with tooltips to clarify the namespaces and everything linked to ease exploration. The few semantic explorers I’ve tried that try to expose semantics in the query turn every result into a “facet explorer” and are hard to grasp.

On the search aspect, apart from giving new constraints natures for advanced user, i fail to see any real advantages.

The ability to jump from entity to entity, knowing the nature of their connection (written by, owned by, mother of) is the real pervasive UI inovaltion.
A Generic Entity Viewer providing hyperlinks and/or thumbnails to linked entities with a human readable/translatable description of the relation could be, if well designed, a real gain of productivity for the user.
The view could be customized for known entity types.
Imagine it connected to the Semantic Web transparently to the user.

And actually some web-based tools od just that for the Semantic Web using SPARQL and RDF. Some code might be useful there, if not all :)

Besides, in the Conclusions section I did *exactly* what you asked for.