Subject: PaceAllowDuplicateIDs alteration

From: Graham <[email-masked]>
Date: Fri, 6 May 2005 15:09:10 +0100

As the WG may have noticed, I have some serious problems with the  
Pace. One small change would eliminate about 75% of them:

Replace the line:

"If an Atom Feed Document contains multiple entries with the same  
atom:id, software MAY choose to display all of them or some subset of  
them"

with:

"If an Atom Feed Document contains multiple entries with the same  
atom:id, software MUST treat them as multiple versions of the same  
entry"

I don't think this changes the technical meaning of the proposal, but  
does make it very explicit.

Would anyone object to this change?

Graham

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From: Brett Lindsley <[email-masked]>
Date: Fri, 06 May 2005 09:35:22 -0500

What determines a "version"? If we have multiple entries with identical 
information,
these are copies, not versions.

The real issue is feed state. Given there are identical IDs, can we 
determine if
the entries are identical or different? The end client can then deal 
with it any way
it wants (e.g.):
- Keep only the most recent.
- Display them all.
- Combine them all into a single entry with a history.
- Show changes.
- Drop duplicates.
- etc.

Sorry I don't have an answer here, just an observation of the exact problem.

Brett

---

From: Tim Bray <[email-masked]>
Date: Fri, 06 May 2005 07:37:59 -0700

> atom:id, software MUST treat them as multiple versions of the same 

Hmmm; the Pace already says "If multiple atom:entry elements with the 
same atom:id value appear in an Atom Feed document, they represent the 
same entry."  So what you want is almost there.

> does make it very explicit.

My problem is that when you say "software MUST", I think you should 
follow up with something specific and testable.  This assertion feels 
fairly vague and leaves room for lots of argument.  Maybe a first step 
to tightening it up would be to provide some specific examples of 
software behaviors that would be forbidden/allowed by this MUST-clause.

-Tim [who has yet to express a +1 or any other final opinion about this 
Pace]

---

From: Eric Scheid <[email-masked]>
Date: Sat, 07 May 2005 00:52:19 +1000

> does make it very explicit.

+1, with one minor amendment.

    s/versions/instantiations/

the spec uses that word elsewhere, and 'versions' might suggest a media
adaptation, language variant, etc.

e.

---

From: "Bob Wyman" <[email-masked]>
Date: Fri, 6 May 2005 11:16:45 -0400

Graham wrote:
> "If an Atom Feed Document contains multiple entries with the 
> same atom:id, software MUST treat them as multiple versions of
> the same entry"
	Are they still the same entry if they have different source elements
that identify their source as being different feeds? 

		bob wyman

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From: Bill de hÓra <[email-masked]>
Date: Fri, 06 May 2005 16:16:03 +0100

Graham wrote:
> 
> As the WG may have noticed, I have some serious problems with the  Pace. 
> One small change would eliminate about 75% of them:
> 
> Replace the line:
> 
> atom:id, software MUST treat them as multiple versions of the same  entry"
> 

Looks promising. Would you replace "versions" with "representations"?

cheers
Bill

---

From: Eric Scheid <[email-masked]>
Date: Sat, 07 May 2005 01:49:04 +1000

> that identify their source as being different feeds?

I don't see why. I subscribe to a Local News feed, a National News feed, and
a Science News feed. All from the same publisher. The same story may appear
in one, two, or three of those feeds. I don't believe each of those feeds
would have the same feed/source values.

e.

---

From: Robert Sayre <[email-masked]>
Date: Fri, 6 May 2005 13:49:28 -0400

> that identify their source as being different feeds?

I would say yes. Entries IDs are globally unique. If they aren't the
same entry, it's a collision, right?

Robert Sayre

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From: Tim Bray <[email-masked]>
Date: Fri, 06 May 2005 10:53:14 -0700

> would have the same feed/source values.

Right.... but the story's <atom:entry> would have the same atom:id in 
each of those feeds, right?  So they are the same entry, right? -Tim

---

From: Graham <[email-masked]>
Date: Fri, 6 May 2005 18:34:10 +0100

> that identify their source as being different feeds?

Why wouldn't they be? It would mean "Here's how the entry looked when  
it was published in feed A" and "Here's how the entry looked when it  
was in feed B". But if the publisher has assigned them the same ID,  
that's a fairly clear expression that they're versions of the same  
thing.

(obviously there's the danger of spoofing, but that's a general  
problem with IDs and not something that needs to be noted in every  
sentence)

Graham

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From: Antone Roundy <[email-masked]>
Date: Fri, 6 May 2005 15:27:32 -0600

> that identify their source as being different feeds?
In a perfect world with no malicious, undereducated, misinformed, 
intellectually challenged or other people people who don't mint ids 
appropriately, yes, they're the same entry.  In the real world, I have 
no idea.  A human looking at them could probably determine whether 
they're the same if they're different enough, but if they're 
substantially similar, then even a human wouldn't necessarily be able 
to determine whether they're the same or whether one is a malicious 
alteration.  There's no automated way to decide (unless their contents 
are identical).

Authors of consuming applications will have to decide whether or not to 
obey the commandment from the spec (if adopted) to treat them as being 
the same, or whether to give their users the option of making that 
decision.  Specifying that publishers who publish the same entry in 
multiple feeds MUST choose one to be the "original" source and express 
the rest as aggregated entries from that feed would make it much easier 
to justify treating them as different entries if they claimed to 
originate in different feeds.

---

From: Eric Scheid <[email-masked]>
Date: Sat, 07 May 2005 18:45:51 +1000

On 7/5/05 3:53 AM, "Tim Bray" <[email-masked]> wrote:

>>> Are they still the same entry if they have different source elements that
>>> identify their source as being different feeds?
>>> 
> Right.... but the story's <atom:entry> would have the same atom:id in each of
> those feeds, right?  So they are the same entry, right? -Tim
> 

typo: "I don't see why not."

d'oh!

(Tim: yes)

e.

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From: David Powell <[email-masked]>
Date: Fri, 13 May 2005 01:20:02 +0100

> adaptation, language variant, etc.

How about "revisions"?

"versions" could sound too broad, it could imply that the entry could
change for all sorts of reasons, conneg etc.

"instantiations/instances" could sound like they could be identical
copies of the same information.

"revisions" suggests something that changes over time, which is closer
to what we mean I think?

-- 
Dave