I think we're on the same page(?)

So do I.

The point I was trying to make was about the mechanism by which we assign
IPs to a server in OCCI. I think that the assigned IP(s) should be specified
an attribute of the link between the server and the network.

Well the process depends on the protocol but yes an IP needs to be assigned to a specific link between a server and a network. Another reason why addresses as first class citizens doesn't work (links having associations to resources starts to get fugly). Storage resources can have IPs by the way, as can network devices (but not sure it makes sense for network resources - will see that in due course).

CIDR notation's another thing to think about at some point, especially for offering up large numbers of IPs - and yes I know it gets hairy fast.

A less detailed version would be like the last paragraph: just list the
assigned IP(s) as attributes of the link.

That's what I would be expecting to see - one attribute for each IP.

A more detailed version with better support for multiple IPs (e.g. for SSL
web hosting) would be like my original e-mail in this thread and distinguish
between two type of IP assignment:
1) A potentially large set of IPs which the server is permitted to use
(i.e. all of the SSL web hosting IPs which they have purchased)
2) A single IP which is the primary IP to tell the server if it sends a DHCP
request

We need to be really flexible here - inflexibility will result in a> serious problems for users and/or b> seriously ugly workarounds. Addressing elements (XML parlance) hanging off resources and specifying the interface as an attribute may offer more flexibility than trying to do them as attributes on the links. Whatever gives the most flexibility...

Sam