[Kde-pim] [Akonadi] Virtual Collections

[Volker Krause]

On Sunday 13 September 2009 11:26:18 Eduardo Robles Elvira wrote:
> Sorry for the late answering, I'm at the moment quite busy with the
> september exams (I'll finish the 21th). I've read the whole wiki and
> it seems that konqueror bookmarks is not the only case anymore in
> akonadi where the backend for storing the data is Nepomuk itself, now
> that we have the Tag resource (which I didn't know it existed anyway
> previously).
>
> If I understand correctly, the idea is to have virtual collections in
> a different resource than the one used for non-virtual collections? I
> don't really see the need for that.

The main reason for not mixing them is that they cannot be persisted by any 
known resource so far. Eg. if I can create a virtual collection within my 
IMAP folder tree, I would expect it is stored on the IMAP server, which of 
course does not work. To avoid that confusion we introduced the strict 
separation between those two.

> Also, I don't understand very well 
> the difference between physical virtual resources and virtual virtual
> resources :P

That's mostly a theoretical construct to make the whole plan consistent ;-) I 
would like to get rid of that eventually, it certainly wont show up anywhere 
outside of the server.

> As an use case for virtual resource we could have Konqueror bookmarks.
> There you want to have virtual collections like "most visited
> websites", "recently added bookmarks" or "unclasified bookmarks". Also
> you want the awesome bar to search bookmarks. For searching bookmarks
> in the awesomebar I maintain a bookmarks model and a custom filter
> proxy model, which is probably faster/more efficient than creating a
> virtual collection, modify the query on the go depending on the user
> input and watch changes in the virtual collection.
>
> But for virtual collections like those I mentioned probably a
> persistent search query would fit best. So for search I would suggest
> using Nepomuk and for the query language those nepomuk supports
> (Sparql?). I've got the nepomuk sparql queries for some of those
> virtual folders but last time I checked the search folders were not
> working to me. 

That's the plan, getting virtual collections as such to work correctly is the 
first step there, persistent search is then one usecase for them.

> Anyway, I would like to let the user put those search 
> queries wherever in the hierarchy of the bookmarks resource he wants,
> and currently Akonadi doesn't support that.

That's indeed a valid usecase, and I don't really see technical problems with 
that, but I'm unsure if users will understand such mixed trees correctly.

> For me, a compromise solution would be to put a placeholder folder
> saying "here goes the recently added bookmarks virtual collection" and
> then manually put it there in my bookmarks model. This would let the
> user put the virtual collection in multiple places if he wants .This
> is what I plan to do at the moment (when I get search collections
> working again), but perhaps we could come up with a better solution
> within Akonadi itself?

Sure this can be emulated on the client side, but if we have applications 
doing that, we can as well do it on the server side, which should be much 
easier I think.

regards
Volker
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