Re: [syndication] RSS Referencing

[Sam Ruby <rubys@intertwingly.net>]

Stephen Downes wrote:
> RSS Referencing
> Stephen Downes
> July 27, 2005
> 
> 0. Disclaimers
> 
> - Maybe this discussion has already taken place somewhere. But if so,
> I haven't seen it, and pointers would be appreciated. 
> 
> - Terminology used below is RSS terminology, however the same points
> are intended to be applied to Atopm.
> 
> 1. The Disappearing Reference
> 
> Back at the beginning, an RSS item had three major elements: title,
> description and link. What to put in the first two of these was always
> reasonably clear. However, an ambiguity existed with respect to the third.
> 
> The link element was taken to contain a URL for the item being
> described in the title and the description. This created two
> possibilities: whether the link pointed to one's own article, or
> whether it pointed to an article written by a third party.
> 
> For example, the RSS for the New York Times might contain a list of
> articles, and the link for each item would point to the URL of the New
> York Times article, everything being in the nytimes.com domain.
> However, the RSS for Fred's Big Links might point to articles from
> many newspapers, the link in one pointing to nytimes.com and another
> to wapost.com and so on.
> 
> When software such as Blogger and LiveJournal embraced RSS, they
> embraced the first model. Thus, every link in every item in the feed
> generated by halfanhour.blogspot.com pointed to an article within the
> halfanhour.blogspot.com domain. RSS, therefore, was thought as a site
> summary document, rather than a linking document.
> 
> Over time this has become the dominant model for RSS; my own RSS feed
> - http://www.downes.ca/news/OLDaily.xml - is one of the very few feeds
> left in the world listing feeds outside the feed domain. Almost all
> feeds point to a page within their own domain. However RSS
> aggregators, such as Daypop, PubSub and Syndicate, provide RSS feeds
> with external links in the link element (as one would expect).
> 
> But what if we want to do both? What if we want to, say, create a post
> in Blogger that talks about an external resource, such as an article
> in the NY Times? It seems that we must pick one of the two possible
> links - the blogspot.com link or the nytimes.com link - to put into
> the link element. Blogger, of course, makes the choice for us, placing
> the blogspot.com link into the link element. But now, crucially, the
> nytimes.com link disappears from the RSS (or the Atom, as both have
> this problem).

Actually, I think that you have effectively reconstructed the history
behind why the atom:link is what it is.

Take a look at this presentation from 2003:

http://intertwingly.net/slides/2003/xmlconf/22.html
http://intertwingly.net/slides/2003/xmlconf/23.html
http://intertwingly.net/slides/2003/xmlconf/24.html
http://intertwingly.net/slides/2003/xmlconf/25.html
http://intertwingly.net/slides/2003/xmlconf/26.html

The key point is that in Atom, an entry can have multiple links.  Each
link defines the type of relation via a simple attribute.  The default
for this attribute is "alternate", which (as you indicate) is the
predominant use for this in RSS 2.0 today.

The values that Atom has initially registered for rel values has changed
from that 2003 presentation, and can be found in section 4.2.7.2 of
http://www.ietf.org/internet-drafts/draft-ietf-atompub-format-10.txt;
but in any case there is a process by which one can register new rel
values, either that or you can define your own as a fully qualified URI.

Finally, it is quite legal to put elements in other namespaces into RSS
2.0 feeds, and some have advocated doing exactly that:

http://support.journurl.com/users/admin/index.cfm?mode=article&entry=920

- Sam Ruby