[Wasabi] Kicking of the Metadata spec - brainstorm

Mikkel Kamstrup Erlandsen mikkel.kamstrup at gmail.com
Tue Feb 20 14:25:54 PST 2007

2007/2/20, Jos van den Oever <jvdoever at gmail.com>:
> 2007/2/20, Joe Shaw <joeshaw at novell.com>:
> > Hi,
> >
> > On Tue, 2007-02-20 at 20:52 +0100, Jos van den Oever wrote:
> > > But reading, writing and searching metadata fields is something that
> > > desktop applications will want to do more and more. Since there is, to
> > > my knowledge, also no standard for reading and writing metadata in
> > > fd.o, this is a good opportunity to come up with it.
> >
> > I agree.  But it is something that should be kept conceptually separate
> > from desktop search.
> >
> > > Whereas we are talking about metadata that relates to files, they are
> > > working on a wider definition.
> >
> > Do you mean files in their strictest sense, or also things like emails,
> > addressbook contacts, etc?
> Yes, those too. Mails are clear, addressbook contacts is a bit
> slippery, but yes those too. So files and url-addressable parts of
> files.
> >
> > > When you think of writing metadata, you can e.g. think of the
> > > properties dialog in Konqueror where you can write title and artist
> > > for mp3 files. For searching you want to name this field and for the
> > > read/write api you want to name it too, so you might as well use the
> > > same language for that.
> >
> > Indeed, and we should also use the same storage for it whenever
> > possible.  I envision a three-tiered system for actually setting
> > metadata on files:
> >
> > 1. Store the metadata in the file itself whenever possible.  Things like
> > id3 tags in MP3s or XMP metadata in jpegs.  This is ideal because it's
> > in a standardized format that most tools can read, and the metadata
> > follows the file around no matter where it's sent.
> >
> > 2. Store metadata in extended attributes on the file in the file system.
> > This has the benefit in that the metadata follows the data around within
> > a single system, and our desktop applications can be standardized around
> > a schema for xattrs.  Obviously this won't work for non-file items or on
> > file systems that don't support them.
> >
> > 3. Lastly, store metadata in some sort of centralized store, like a
> > sqlite database.  Keeping metadata in sync with data is harder, but
> > fortunately most of the data that would require this mechanism wouldn't
> > have mostly unique URIs.  I'm sure Jamie will disagree with me on this,
> > but I don't think this requires a constantly running daemon; a simply
> > library interface would probably suffice.
> Hehe, now _you_ are taking this spec further then intended. ;-)
> I'll not get into this. On the KDE side this is something for
> Sebastian Trueg (Nepomuk) to consider.

Is it just Sebastian? I'm generally not keen on one-man-speccing.

I can't make up my mind. On one hand I think that the way metadata is stored
is an implementation detail, on the other hand it might be good to
standardize it. It could be a standard that is orthogonal to the other parts
of the metadata specs though.

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