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Re: Input on request for link relation

From: Jan Algermissen <algermissen1971@mac.com>
Date: Fri, 11 Sep 2009 01:57:48 +0200
Cc: Lisa Dusseault <lisa.dusseault@gmail.com>, Atom-Syntax Syntax <atom-syntax@imc.org>, ietf-http-wg@w3.org
Message-id: <C86DEC0A-6370-4C0B-98A9-3806F2014AE5@mac.com>
To: jpanzer@acm.org

On Sep 11, 2009, at 1:31 AM, John Panzer wrote:

> Without getting into the appropriate discussion form question, what  
> hub resource semantics (and link relation definition) are you  
> referring to exactly?  I can't seem to find it, and it's hard to  
> understand your objection without it.

Section 7.3 says:

"If, after a content fetch, the hub determines that the topic feed  
content has changed, the hub MUST send information about the changes  
to each of the subscribers to the topic."

I understand this to imply that subscribers expect the hub to  
definitely send the notifications. What if the hub decides not to due  
to the number of subscribers it has? Or to turn this around: how would  
a subscriber ever know whether not receiving notifications means that  
there are not updates or that the hub stopped sending notifications.

Jan



>
> On Thu, Sep 10, 2009 at 12:40 PM, Jan Algermissen <algermissen1971@mac.com 
> > wrote:
>
> Lisa,
>
> not sure the following it is appropriate to discuss this here, so  
> please redirect me to the proper place if so.
>
> Hubs are being discovered by clients by way of the 'hub' link  
> relation. I am
> concerned that the semantics of a hub resource (provided by the link  
> relation
> definition) are imposing obligations on the server that are contrary  
> what one
> would expect to see in the HTTP world.
>
> Or in other words: I think that the assumptions a client makes about  
> the behaviour
> of a hub are too rigid. If a hub has more subscribers than it knows  
> it can handle
> it might well decide not to notify them. A situation like this is  
> impossible to
> prevent by the specification and I think the server should therefore  
> explicitly be
> given much more freedom regarding its behavior upon a ping.
>
> Especially given the use of Atom which in a sense implies a very  
> unconstrained
> protocol.
>
> (Sorry if this discussion is already going on elsewhere)
>
> Jan
>
>
>
> On Sep 10, 2009, at 7:30 PM, Lisa Dusseault wrote:
>
>
> Comments welcome on the following request
>
> thx,
> lisa
>
> ---
> General Request for Assignments (link-relations)
>
> Contact Name :
> Brett Slatkin
>
> Type of Assignment :
> I want to add a new Atom Link Relation type for the PubSubHubbub  
> protocol
>
> (http://pubsubhubbub.googlecode.com). The relation type is "hub".
>
> Registry :
> http://www.iana.org/assignments/link-relations/link-relations.xhtml
>
>
> Description :
> The new  is used for discovery of Hubs,
> which enables real-time notifications of entries in Atom and RSS  
> feeds.
> Without making the relation type official, we're not in compliance  
> with the
>
> Atom spec.
>
> Additional Info :
> http://pubsubhubbub.googlecode.com/svn/trunk/pubsubhubbub- 
> core-0.1.html
>
>
>
Received on Thursday, 10 September 2009 23:58:36 GMT

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