From mboxrd@z Thu Jan  1 00:00:00 1970
From: Doug McIlroy <doug@research.bell-labs.com>
Message-Id: <200112081958.OAA264525225@nslocum.cs.bell-labs.com>
To: rob@research.bell-labs.com, 9fans@cse.psu.edu
Subject: [9fans] Python filesystem
Date: Sat,  8 Dec 2001 14:58:52 -0500
Topicbox-Message-UUID: 3150e41c-eaca-11e9-9e20-41e7f4b1d025

I
I don't know what it has to do with Python, but
here's a little about the half-baked idea referenced in
the attached message.
In its simplest form, the idea was for the metadata
to be a single line of text, with all the metadata
in a file system unioned into a single file in which
each line begins with the (or a) name of the
associated data file.  What descriptors might
go in the metadata is left arbitrary.
To ask about a file, one would just look at the metadata.
To find a file given some descriptors, one could grep
the union file.
I never thought of an appealing way to maintain the
union file.  How, for example, can a useful name
be determined for a file, short of some ugly AI
like pwd?  What happens to the metadata when
a file gets recreated?  Assuming only one copy
of metadata exists for a file with two names, how
do you treat the metadata on unlink?
One can come up with answers to these questions, but
can one come up with a solution that will run fast
and be accurate?
Glimpse, for example, provides (a different sort of)
index to the contents of a file system by periodically
reading the whole file system.  Hence it cannot be
accurate.
The way metadata is stored matters, too.  Imagine
trying to grep the union of 10,000 files, were
each metadata item in a separate file.
If anybody thinks up a good way to overcome the
problems, I'd love to hear about it.

Doug McIlroy


>From: skipt@real.com
>Date: Thu Nov 29 14:50:26 EST 2001
>To: 9fans@cse.psu.edu
>Subject: Re: [9fans] Python filesystem
>
>In a thread long ago, Rob mentioned an idea proposed by Doug McIlroy for an
>indexed/annotated filesystem that would keep an annotation file for each
>regular file. It would seem like the right idea for keeping the mod
>documentation, etc.
>
>BTW, I've not been able to find any reference to the annotation/fs idea.
>Was anything written up (that could be shared)?
>
>>What do we lack then?  Locking and management of metadata?  There's
>>probably a way around those, as well.  The revision control FS isn't
>>well formed for saving; maybe a better solution would be to echo a
>>revision number into a ctl or new file, and then have that create a new
>>delta.  Write the file into it, and let the FS take care of picking out
>>the delta and storing it.  Perhaps a metadata file could be associated
>>with every file.  eg, foo.c;meta, foo.c;1.0, etc.
>