Subject: Re: Atom, files and directories: what it's all about

From: Uche Ogbuji <[email-masked]>
Date: Thu, 01 Dec 2005 09:50:20 -0700

On Tue, 2005-11-29 at 10:25 +0100, Henry Story wrote:
> On 29 Nov 2005, at 00:31, Luke Arno wrote:
> > On 11/28/05, Ernest Prabhakar <[email-masked]> wrote:
> >>
> >> Hi Henry,
> >>
> >> On Nov 23, 2005, at 3:22 AM, Henry Story wrote:
> >>> A few improvements of atom over directories is that our feed can
> >>> contain not just the current version of an entry, but all previous
> >>> versions as well, which I think I remember was a feature supported
> >>> by the vms file system.
> >>
> >> Interesting.  It reminds me of a thought I had a while ago:  would it
> >> be possible to emulate 80% of WebDAV by using HTTP + Atom?

> I think that is very much the idea. If you check what is going on on  
> the atom protocol group you will find that they are moving in that  
> direction
> 
> http://bitworking.org/projects/atom/

Hmm.  I worry about such a land grab.  I'd rather put muscle behind
WebDAV and be sure that Atom dovetails.  I think that the similarities
should be used to ensure such dovetailing, rather than to seed a
competition between Atom and DAV.

> >> Would we
> >> also need some sort of list structure, a la XOXO?
> >>
> >> http://microformats.org/wiki/xoxo
> >>
> >
> > Yup, but Atom Feed _is_ a list format. :-)
> 
> Mhh. An Atom feed is a *Set* of entries. Not a list of entries.
> The entries are not ordered in any particular way in a feed. That is  
> stated in the spec section 4.1.1
> 
> [[
> This specification assigns no significance to the order of atom:entry  
> elements within the feed.
> ]]
> 
> In this sense it is again like the files in a directory. You can sort  
> them different ways using options to the ls command, or if you have a  
> graphical browser by clicking the different columns, but there is no  
> objectively better order than another.

I was going to mention this.  I will say that the available convention I
know of for allowing ordering is the feed rank proposal

http://www.ietf.org/internet-drafts/draft-snell-atompub-feed-index-03.txt

But I think it's a bit clumsy to stretch this approach beyond simple
ranking.  Maybe a more general purpose extension for collation algorithm
overlay is in order?

> In html one could perhaps represent them as un unordered list, which  
> is perhaps what the xoxo people intend.

The XOXO people intend both.  <ol> for ordered lists.  <ul> for
unordered lists, just as in Uncle XHTML.

> > You should check out some of the recent introspection
> > discussion that went on over on Atom Pub.

Man.  I just barely convinced myself to muster the non-existent spare
time to follow this list (I've been lurking for a week now).  So many
lists, so little time.

-- 
Uche Ogbuji                               Fourthought, Inc.
http://uche.ogbuji.net                    http://fourthought.com
http://copia.ogbuji.net                   http://4Suite.org
Articles: http://uche.ogbuji.net/tech/publications/

---

From: Henry Story <[email-masked]>
Date: Thu, 1 Dec 2005 18:35:43 +0100

> competition between Atom and DAV.

I don't think this need be thought of as a landgrab.

For one it is probably a consequence of atom trying to do the  
simplest thing possible. When you think about it, a file system or  
directory hierarchy is probably one of the simplest things around. It  
is not surprising that if you think about content and publishing  
content you end up with something that is very very similar to what  
we had before.

Secondly Atom is already finished. It can hardly be claimed that atom  
(and all the RSS formats before it) tried to grab hold of something  
unintentionally. 'Grabbing' involves a conscious act, an intention.  
If you think of Atom as a mathematical structure which in some sense  
it is (if you follow some of the work of the atom-owl group) then you  
are closer to understanding the type of grabbing that is happening  
here. It is just simply that there is a strong isomorphism between  
these two structures [1]. You and me are very similar. We are both  
human. And there is an isomorphism there too. But I never intended to  
grab you :-)

Mentioning WebDav further reinforces the parallel with file systems  
now that I think of it. If you look at the parallel between atom and  
WebDav, and compare this with the parallel between a plain unix file  
system and a metadata enabled one, we have a very illuminating  
parallel. A plain file system is the simplest thing around pretty  
much and as a result it is the most wide spread type of file system.  
Atom and RSS follow a similar pattern. They are much more widely  
available than WebDav implementations. WebDav on the other hand is  
really very similar to the metadata enabled file systems such as the  
one shipped with Apple's Tiger [2]. In WebDav you ask the file  
directly for its properties using PROPGET; in Tiger you do that using  
tools such as xattr.

% xattr --set name John file
% xattr --set color red file

% xattr --list file
file
         color   red
          name   John

So with this paralell in mind

	Simple File System  / Atom
	Metadata File System / WebDav
	
it becomes possible to further see how there is no landgrab happening  
at all. Notice that both normal file systems and metadata file  
systems can coexist quite peacefully. In fact OSX allows you to copy  
a file with metadata to a non metadata enabled file system without  
trouble and without loosing your metadata. Furthermore I imagine it  
would be quite possible to publish atom files to WEBDAV systems.

Certainly it would be interesting to look into these parallels further.

Henry Story

[1] http://en.wikipedia.org/wiki/Isomorphism
[2] http://arstechnica.com/reviews/os/macosx-10.4.ars/7

---

From: Uche Ogbuji <[email-masked]>
Date: Thu, 01 Dec 2005 13:20:17 -0700

> I don't think this need be thought of as a landgrab.

It needn't be, of course, but I think your characterization so far gave
the impression that it could be.  Nevertheless, I think I'll leave off
this thread.  After all, it's all vapor so far, and so no real problem.
If people do start coming up with WebDAV-replacement ideas, and
seriously advocating them, I can take up the cause then.  Until then,
it's all academic.

I will say while ducking through the door (sorry) that I don't think the
distinction between "simple file system" and "metadata file system" is
all that instructive, but again I'll have to take up that matter if it
comes up again in a more practical context.

---

From: Henry Story <[email-masked]>
Date: Thu, 1 Dec 2005 23:27:51 +0100

Thanks Uche for making me think a little more carefully about this  
topic. Your intervention has been very helpful in identifying a  
concern that is probably more widespread than openly acknowledged.

> seriously advocating them, I can take up the cause then.  Until then,

Seeing something as something else is a very important aspect of  
learning. This reminds me of various mathematical puzzles one learns  
in school. It is a long time since I studied geometry but I can  
remember the importance of seeing a shape as the sum of two others.  
Was it by these means that the Greeks prooved the irrationality of  
the square root of 2? [1] I can't remember. But there are many other  
examples along these lines, I am sure. These questions may be  
academic, but one should not disparage academia. It is from those  
quarters that some of the greatest changes in the human condition of  
stemmed from.

> comes up again in a more practical context.

If the only practical effect this discussion may have is help people  
think about feeds a little differently, something will have been  
achieved.

Thanks again for participating,

	Henry Story
	http://bblfish.net/blog/

[1] http://en.wikipedia.org/wiki/Irrational_numbers#Another_proof