[Nepomuk] NMM, music ratings and muzicbrainz ID

[Roman Evstifeev]

Hi list. I'm trying to resolve a problem of organizing user's music metadata.

Let's say i want o write an application, that will allow to keep track
of user's music ratings, playcounts, tags and so on.

Problem number 1:
User can have the same audio file in flac and in mp3 on the same machine
In my app i want to allow user see all of them, and rate them as one -
i.e. to rate music tracks, but not the files themselves.
The point is - there should not be a situation, where two files,
representing the same music track will have different ratings.
nmm:MusicPiece is subclass of nie:InformationElement, and it is in
domain of nfo:codec.
So essentially i should have 2 MusicPieces (each having its own
codec), and rate some other resource, which links to them both.

Possible solution (suggested by phreedom) :
Declare a new Class. subclass of pimo:Thing, wich will represent a
music track. (let's name it pimo:MyMusicPiece)
Then create instance of it, rate it, and link it to the relevant
MusicPieces as a pimo:groundingOccurence_s of that thing

but there is another problem:

Problem numer 2:
There may not be a file at all.
I want to allow user to have metadata about music, that is not
represented by any local (or remotely accessible) file.
(usecase: i have a vinyl disk on shelf, and want to share my opinion
about it with friends (for ex. rating). i don't have any file.)
I surely want to also keep general data about this music as: Artist,
Title and possibly muzicbrainz ID.
Currently nmm:musicBrainzTrackID property is in domain of nmm:MusicPiece
This raises few questions:
1) Should nmm:MusicPiece(nie:InformationElement) have a relevant
file(nie:DataObject?) at all?

If so, there is a Possible solution 1:
i can make my pimo:MyMusicPiece instances also nmm:MusicPiece_s
without them representing any particular file.
Then i can apply properties such as nmm:musicBrainzTrackID, nmm:composer to it.

Possible solution 2:
Create my own properties, resembling nmm:musicBrainzTrackID and
nmm:composer, but in domain of my pimo:MyMusicPiece.