Note that this isn't actually accepted as-is, see http://imc.org/atom-protocol/mail-archive/msg03718.html
Consider the order of <collection> elements in the workspace to be significant. The first element SHOULD refer to the preferred|default|primary collection
Merged with PaceReworkIntrospection
Provides a simple solution for indicating the preferred|default|primary collection within a <workspace> without conflating default collections with nested collections (which serve two completely different purposes).
It works for autodiscovery
Add the following sentence to the draft -06 section 7.3.2
"The order of 'app:collection' elements is significant. The first element SHOULD refer to the preferred or primary collection."
In the following example, "Entries" would be considered the "preferred" or "primary" collection
<service> <workspace title="My Blog"> <collection title="Entries" ... > <collection title="Photos" ... > </workspace> </service>