For those of you who read my last post ("More on capabilities and RNA"), I
am looking to trade "capability URIs" up front instead of relying on the
query mechanism (which I hope to get rid of altogether). In order to do
this, there are basically three possible patterns I want to support:

1) Sender and reciever trade capability URIs. This is good for general
two-way notifications such as e-mail, forums, etc.
2) Sender gets capability URI from receiver. This is good for situations
where a sender wants to push notifications,but not get them. For instance,
this could be used to do things like submit entries to a search engine,
aggregator, etc.
3) Receiver sends capability URI to sender. This is good for situations
where a recipient wants to "subscribe" to read-only notifications. For
instance, this could be used to receive stock quotes, news headlines, etc.


Ideally, I would like to come up with a pattern for #1 which encompasses #2
and #3.

Also, these capability URIs must be guarnateed to match the general RNA
URIs. In other words, if I (http://seairth.com/rna) were to receive a
capability URI (http://rnaserv.net/bob/2342344) from Bob
(http://rnaserv.net/bob), Bob must be sure that I was the one who received
the capability URI and I must be sure that Bob is the one who gave me the
capability URI (ignoring eavesdroppers). This should be true both ways.

Here are my thoughts so far. Please feel free to tear them apart!

If I POST to http://rnaserv.net/bob returned a capability URI, I would know
that relationship between his URI and his capability URI was valid.
However, Bob would not know the same between my URI and his capability URI.

If I POST to http://rnaserv.net/bob, which causes Bob to turn around and
POST the capability URI to http://seairth.com/rna, then Bob would know the
relationship to be valid, but I would not.

In other words, the only way I can validate the relationship is if the
capability URI returned in response to the first POST, while Bob must rely
on the valid connection of the second POST to validate the relationship.

So, the only way I have thought of so far is a two-phase exchange:


Solution To Pattern #1:

Phase 1: I POST http://seairth.com/rna and http://seairth.com/rna/12345 (my
capability URI) to http://rnaserv.net/bob. I get back a response containing
my original entries plus http://rnaserv.net/bob and
http://rnaserv.net/bob/44953324 (Bob's capability URI). At this point, I
can assert the relationship between his URI and his capability URI are
valid.

Phase 2: Bob POSTs the same document that was returned in the last response
to http://seairth.com/rna. If it is valid, I return the document back
again. At this point, because I have confirmed the document, Bob can be
sure of my own relationships between my URI and the capability URIs (both
mine and his). If it is not valid (because I recognize that I did not issue
http://seairth.com/rna/12345, for instance), I return an error (which HTTP
response code?), which tells Bob that something was wrong and that he should
probably invalidate his own capability URI (as well as not use the one I, or
someone impersonating me, sent him in the first place).


Solution To Pattern #2:

Phase 1: I POST http://seairth.com/rna to http://rnaserv.net/bob. I get back
a response containing my original entry plus http://rnaserv.net/bob and
http://rnaserv.net/bob/44953324 (Bob's capability URI). At this point, I
can assert the relationship between his URI and his capability URI are
valid.

Phase 2: Bob POSTs the same document that was returned in the last response
to http://seairth.com/rna. If it is valid, I return the document back
again. At this point, because I have confirmed the document, Bob can be
sure of my own relationships between my URI and the his capability URIs. If
it is not valid (which would be unlikely), I return an error (which HTTP
response code?), which tells Bob that something was wrong and that he should
probably invalidate his own capability URI.


Solution To Pattern #3:

Phase 1: I POST http://seairth.com/rna and http://seairth.com/rna/12345 (my
capability URI) to http://rnaserv.net/bob. I get back a response containing
my original entries plus http://rnaserv.net/bob.

Phase 2: Bob POSTs the same document that was returned in the last response
to http://seairth.com/rna. If it is valid, I return the document back
again. At this point, because I have confirmed the document, Bob can be
sure of my own relationships between my URI and my capability URIs. If it is
not valid (because I recognize that I did not issue
http://seairth.com/rna/12345, for instance), I return an error (which HTTP
response code?), which tells Bob that something was wrong and that he should
not use the capability URI I, or someone impersonating me, sent him in the
first place.


You will notice that Phase 2 is pretty much the same in all three cases.
The only difference is who passes a capability URI in Phase 1. So... what
do you all think? Does this work? Is it RESTful? Is there a better way?

---
Seairth Jacobs
seairth@...