Re: Updated metadata proposal
- From: Tom Tromey <tromey cygnus com>
- To: Christopher Curtis <ccurtis ee fit edu>
- Cc: Tom Tromey <tromey cygnus com>, Gnome Mailing List <gnome-list gnome org>
- Subject: Re: Updated metadata proposal
- Date: 26 Aug 1998 23:14:08 -0600
Christopher> a) making 'fast' the default
>> I disagree. In general `fast' lookups should only be made when the
>> programmer knows this is required. It rarely is. So the default
>> should be to do the right thing.
Christopher> I'm sorry, but I find this very confusing.
No problem; I'll try to explain.
Christopher> I would think that by 'fast', you mean a regex or
Christopher> extension type system (*.gif, eg) whereas a non-fast
Christopher> lookup would involve using the 'file' command.
I thought I had addressed this in the document. Anyway, the idea is
that lookups are done in a series of phases. A fast lookup simply
leaves off the final phase, which involves the use of the `file'
command.
The `file' command is actually only used to try to determine the
file's type; the actual metadata in this case is associated with the
type. David Jeske's had an idea to let a metadata lookup be
associated with a given command which could be run to extract the
information. This is a generalization of using `file'. I like the
idea, but I don't plan to implement it. (It could be added later with
only compatible extensions to the API.)
Christopher> Implementation is of course up to you, but this seems
Christopher> like it would incur significant overhead. To me, 'file'
Christopher> lookups would rarely be required.
Since they always follow the other lookups, if they are actually
rarely required then `file' will rarely be run.
>> Sorry. A piece of metadata is just a chunk of raw data. The
>> metadata code doesn't interpret it in any way (except in one
>> special case, the `type' key).
Christopher> This seems limited, but if that's what you want to do ...
Limited in what way? You can store arbitrary data.
Christopher> Are there provisions to open a file using several methods
Christopher> or not?
Christopher> Can a single file be associated with all three above
Christopher> programs using the same method (eg, "open")?
Interpretation of the metadata is up to the user (except for the
"type" metadata -- the implementation itself is a user of this). So
in this case it depends on what "everybody" agrees the interpretation
of `open' will be.
Of course, as I say in my document, whether metadata is used for this
is actually an implementation decision of a different layer. I think
file opening and the like should be handled via CORBA.
Tom
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