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Date: Wed, 12 Dec 2001 02:28:28 +0300
From: Hans Reiser <reiser@namesys.com>
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To: curtis@integratus.com
CC: Anton Altaparmakov <aia21@cam.ac.uk>, Nathan Scott <nathans@sgi.com>,
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Subject: Re: reiser4 (was Re: [PATCH] Revised extended attributesinterface)
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curtis@integratus.com wrote:

>Hans Reiser wrote:
>
>>What I am saying is that each of the N permutations required to
>>transform a file into an extended attribute should be separately
>>selectable.  Theory guys would call this orthogonalizing the primitives.
>> (I am a theory guy.;-) ).
>>
>
>Applying such rigor in the architecture design phase is probably a good
>idea.  Doing it at application run time is not so clear to me.
>
>If you think of files and EAs as apples and oranges, knowing the minimal
>set of orthogonal steps to turn an apple into an orange is good when
>designing, but I hesitate to burden an app with having to select the
>"skin-color" characteristic separately from the "ascorbic acid content"
>characteristic.  IMHO, files and EAs are "package deals" where we have
>chosen a different set of characteristics for each, ones that we believe
>will be useful to an app.
>
>At bottom, a file holds an uninterpreted data stream.  You have to ask
>yourself whether you want that to change or not.  If not, then you
>build any additional functionality in selectable layers on top of the
>filesystem, not in it.  If you do want it to change, then you are
>headed down the path of pulling a database into the filesystem.  Come
>to think of it, I believe that someone is already doing that.  :-)
>
>
>Having an interface such that an app can ask for
>	open("pizza-pie", F_OLIVES|F_PEPPERONI|F_ANCHOVIES|F_PINEAPPLE...)
>where each of the "F_*" options are orthogonal and ask the filesystem to
>layer in a different "filter" between the raw data and the app, or to
>change the access characteristics (eg: block alignment, non-buffered,
>etc), sounds overly complex.  I believe that this would be better done
>by explicitly stacking filesystems in a per-process namespace.
>

#define PIZZA F_OLIVES|F_PEPPERONI|F_ANCHOVIES|F_PINEAPPLE

#define EDIBLE_PIZZA F_OLIVES|F_PEPPERONI|F_PINEAPPLE

Your way allows for PIZZA but not EDIBLE_PIZZA to be selected by users. 
 Both
are easy to specify.  

You cannot know in advance what a user will consider to be EDIBLE_PIZZA. 
 Not allowing choice is for, umh, better I not say what OS likes to 
prevent choice......;-)

Ok, so I understand that what I am advocating is a lot of work, and a 
much harder path to take,
and I understand why you feel you have enough work, and I think we can 
both respect each
other for our positions.

I'll try to convince you again when I have working code that isn't 
monstrous code, but allows
users full choice, ok?

Best,

Hans



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