On 15-Oct-2009, at 12:03, Martin Atkins wrote:
Did you consider simply making an Atom feed of items which themselves
represent feeds? Does this have any disadvantages over the new feedset
element you've defined?
I did; and indeed that’s the initial approach that I took.
However, doing so presented two key difficulties:
1. No grouping of feeds, beyond 'category'. While categories are
useful, they’re a poor fit for representing a hierarchy of nodes
(including the expansion state of the tree).
2. More importantly, though, in order to include the full range of
hint information, one has to overload atom:entry to include all of the
children of atom:feed; moreover, if you wish to provide one or more
“initial” (i.e., hint/advisory/cached) entries, you need to further
complicate matters by embedding sub-entries within the parent.
Thus, I switched tack to defining an atom:feedset and atom:group,
which appeared to offer a couple of key benefits over the above. Most
poignantly, the semantic meaning and syntax of atom:feed and
atom:entry are essentially completely unchanged—they’re merely
interpreted in a slightly different context when they appear within an
atom:feedset. Further, having a different root element makes light
work of determining whether something is a “feed of feeds” or simply a
standalone feed.
I suppose you could boil it down to aiming for the greatest
flexibility with the minimal impact. As atom:feedset can only occur as
the root of a feedset document, the impact upon Atom Feed and Entry
documents is nil. A side-effect of all of this is minimising any
difficulties which might be encountered in modifying Atom document
processors to work with feedsets.
It’s more of a gut feeling, but I think that in order to be *useful*
in most contexts, a user agent would have to be modified to understand
what the purpose of a feedset is, whichever way around it’s
represented (although existing unmodified UAs would certainly be able
to parse a feed where each atom:entry represents another feed, I’m not
convinced that most users would have much use for a subscription to
such a thing!).
All the best,
Mo.
--
mo mcroberts
http://nevali.net
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