Re: GnomeVFS ioctls, live metadata and dead metadata

[Alexander Larsson <alexl redhat com>]

On Tue, 19 Nov 2002, Ian McKellar wrote:

> File stream data and posix metadata are already supported in GnomeVFS. 
> I think that dead extensible metadata would be a worthwhile addition to 
> GnomeVFS - its already in Nautilus but it being in GnomeVFS would make 
> the file-dialog work easier among other things. I think scheme specific 
> metadata needs to be in GnomeVFS by definition because its specific to 
> the different filesystem backends that exist. I'm not sure that 
> format-specific metadata belongs in gnome-vfs. I certainly don't think 
> it can or should be mixed in with other forms of metadata.

I agree.
 
> So I think we need an API in GnomeVFS for dead extensible metadata in 
> gnome-vfs that lets us get/set values on URIs, probably with some other 
> information like modification date (eek - metadata metadata).

And the API has to consider the extended attributes work going on in the 
filesystem. These are used for e.g. ACLs, but could perhaps be used to 
store dead metadata too.
 
> I think that having an API that lets retrieve format-specific metadata 
> would be really cool. Perhaps this could even transparently cache the 
> result in dead metadata. It should be plugin-based so that we can 
> extend it and applications can install handlers for their own 
> file-types.

I don't think it is cool. Nobody has yet been able to say why a generic 
API with add-hoc names and add-hoc parsing of metadata values are better 
than libraries for specific uses.
 
> For scheme-specific metadata we could either provide an additional API, 
> try to fit it in with the dead metadata or try to fit it in with the 
> concept of ioctls. I'm not sure whats best. I guess I would prefer the 
> first option, otherwise we'll end up with a set of standard ioctls for 
> retrieving metadata and those are effectively second-class fileops. Why 
> not just make them fileops?

I think we should make them fileops. But if anyone wants to experiment 
with them outside of gnome-vfs initially they could use an ioctl, then we 
add the real fileops when we merge it.
 
-- 
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 Alexander Larsson                                            Red Hat, Inc 
                   alexl redhat com    alla lysator liu se 
He's an immortal white trash romance novelist on a mission from God. She's a 
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