[Nepomuk] Nepomuk facets

[Sebastian Trüg]

Hi guys,

since you are both working on searching in Nepomuk I wanted to share
some ideas with you (and all interested parties).

IMHO we need a facet system that is flexible in a way that
- it can be used to filter files in Dolphin or in the searchwidget or
  in the query builder (Alessandro: I had the idea that a query builder
  could simply be a search interface which returns the query instead of
  the result.)
- it allows to add custom facets like "recently modified" easily, I am
  not sure if Facet subclassing is required for that but it might be.
  Another approach would be something like a FacetGroup which can be
  populated with a set of Facets that are exclusive (or not) where a
  facet is basically a label and a Term or something.
- it automatically updates when the base query or the selected facets
  change

I was thinking of a FacetModel based on QAbstractItemModel but that is
just one idea. I am not even sure if that is a good one.
SemBrowser currently has Facet as a subclass of QWidget. I am not sure
that is the most flexible approach. IMHO a decoupling of facets from
representation is desirable.
On the other hand something like the DateFacet which allows to choose a
date range can not entirely be done without gui...

Well, let's discuss.

Cheers,
Sebastian