DVFS and Metadata

[Timo Stuelten]

On Sun, 6 Mar 2005, Jamie McCracken wrote:
> It should be plugged in as follows:
> 
> DVFS can check if stuff is up to date by comparing a folder's last changed
> timestamp with the one stored in the metadata DB - If they are identical then
> DVFS can provide metadata direct from the DB whch means something like
> nautilus could become super fast as it wont have to touch every file whenever
> you load a folder (IE it wont have to stat individual files in that folder
> cause it can get a folders contents, thumbnails and properties via the stored
> metadata).
> 
> The metadata stuff would be a seperate daemon so DVFS would need to tell it to
> update stuff if necessary (hopefully with Inotify working smoothly that wont
> happen too often).
So you want to integrate metadata handling completly into the VFS? 

> To index nd extract metadata you would need filters for certain mime types so
> that is no problem (it would be expandable with flter backends).
> 
> ...
>
> Gnome storage is a completely different kettle of fish - it decomposes files
> into a DB and then recomposes them when you access them. Its very difficult to
> get such a system to work without eating your files though so I wouldn't trust
> it :)
Apple does exactly this in its storage subsystem, the same with hibernate and some other java based 
frameworks. To get semantics from structures I think one has to decompose 
files to understand them as documents. For the given 3D-Model example, 
there is now way to handle models flat (i think). But that's not the point. 

What if the MQT changes from simple flat index to a
structure-semantic-someotherfunkymechanism index? To get a thumbnail for a 
folder, there is no need for an enhanced metadata-DB. To get all thumbs 
and compose all with transparency there maybe is. But then you may want  
something more powerful than "thumb.1=aaa.png", "thumb.2=bbb.png" as 
key-value-pairs for the folder.
And if you have this MQT, how to query it? Via getMetadata(folder:="abc", 
key:="thumb.*") from the VFS-API?

The question is: 
Is some Metadata-Query-Thing bound to the VFS or does some MTQ-to-invent 
uses the VFS?
Should the VFS support various MQTs or use a simpler
key-value-based approach with some file-type-metadata-extractor-plugins 
which deliver common metadata using some predefined key and maybe some 
spezialized too.
Should it's features be part of the VFS-API? But then what about Mails, 
IM messages., ...?

As i'm a stupid java developer, i cannot even understand the underlying 
implementation, so no details please. I only want to see an API ;)

-Timo-

-- 
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Timo Stuelten
mailto: t.stuelten at tu-bs.de