Comments below...
Al Brown wrote:
The 01 draft is a much better. I am concerned the generic mechanism
using inlining links is sub-optimal for displaying a hierarchy that
this I-D helps navigate via the new link relations.
in-lining arbitrarily complex hierarchies is always going to be
problematic and suboptimal... which is why I was so adamant about not
baking hierarchy into Atom and Atompub in the first place when we were
working on all this stuff initially. Despite the added verbosity that
this approach adds, however, I think it's likely the most acceptable
approach.
First example: there are two down relations: down and down-tree. It is
important to have both of those link relations on the [standalone]
atom entry that represents a folder so the client can chose a flat
(feed) or tree (expanded feed) representation. If the client chooses
the tree representation, then on the atom feed returned the server
will inline using the link relation down. down-tree is not expanded
with content inline. E.g.,
<atom:entry>
...
<!-- children level 1 -->
<atom:link rel="down" type="application/atom+xml;type=feed"
href="/finance/feeds/default/portfolios/1/positions">
<ae:inline>
<atom:feed>
<!-- /a -->
<atom:entry>
...
<!-- children level 2 for /a -->
<atom:link rel="down"
href="/finance/feeds/default/portfolios/1/positions"/>
...
<ae:inline>
<atom:feed>
<!-- entry /a/1 -->
<atom:entry>
...
<atom:link rel="down"
href="/finance/feeds/default/portfolios/1/positions/down">
<!-- repeats -->
</atom:link>
<atom:link rel="down-tree"
href="/finance/feeds-tree/default/portfolios/1/positions/down" />
...
</atom:entry>
</atom:feed>
</ae:inline>
<atom:entry>...</atom:entry>
<atom:entry>...</atom:entry>
</atom:feed>
</ae:inline>
</atom:link>
<atom:link rel="down-tree" type="application/atom+xml;type=feed"
href="/finance/feeds-tree/default/portfolios/1/positions" />
...
</atom:entry>
The contents of the down link relation will be what should be included
in the down-tree due to recursion through the atom entries. Having a
separate extension element, side-steps this issue of expression.
Hmmm.... I know we've discussed this, but after thinking about it more
and looking through the examples, I'm becoming increasingly less
convinced that we need a distinction between "down" and "down-tree".
One should simply assume that "down" could point to a child entry or
child feed and that those children could potentially also be parents.
Yes, that possibly increases the processing compexity but I think it
simplifies the model overall.
Second example: verbosity
This proposal now has:
<atom:entry>
...
<atom:link rel="down" type="application/atom+xml;type=feed"
href="/finance/feeds/default/portfolios/1/positions">
<ae:inline>
<atom:feed>
<atom:link rel="self"
href="/finance/feeds/default/portfolios/1/positions"/>
...
<atom:entry>...</atom:entry>
<atom:entry>...</atom:entry>
<atom:entry>...</atom:entry>
</atom:feed>
</ae:inline>
</atom:link>
...
</atom:entry>
instead of a simpler mechanism:
<atom:entry>
...
<ah:include rel="down">
<atom:entry>...</atom:entry>
<atom:entry>...</atom:entry>
<atom:entry>...</atom:entry>
</ah:include>
...
</atom:entry>
The I-D introduces a concept of hierarchy through
up/up-tree/down-tree/down relations yet a all-purpose mechanism for
inclusion. Most (all?) of the information on the feed element is
duplicated on the enclosing entry (id, uri, etc). Can't we do better
for this specific scenario the I-D is addressing?
I think we can address this by eliminating the restriction that "down"
and "up" must always point to Atom feed documents and by changing the
cardinality rules for those links. That restriction, I think, is
arbitrary and unnecessary
It would allow us to do something like....
<atom:entry>
...
<atom:link rel="down" type="application/atom+xml;type=entry" href="child1">
<ae:inline>
<atom:entry>...</atom:entry>
</ae:inline>
</atom:link>
<atom:link rel="down" type="application/atom+xml;type=entry" href="child2">
<ae:inline>
<atom:entry>...</atom:entry>
</ae:inline>
</atom:link>
...
<atom:link rel="down" type="application/atom+xml;type=entry" href="childN">
<ae:inline>
<atom:entry>...</atom:entry>
</ae:inline>
</atom:link>
...
</atom:entry>
Unlike any of the other methods discussed, this approach would allow
clients that don't understand the hierarchy model to still understand
that there is some kind of link relationship with each of the individual
child resources and eliminates the need to include the extraneous
atom:feed metadata.
Note that this is the same basic approach taken by my comment thread
extension (in-reply-to).
- James
