Lei,
w.r.t using the anonymous IRI
on non-reply messages - I'd like to point out
that even the WSA spec[1] itself doesn't
adhere to their own "SHOULD NOT".
If you look at the text for wsa:To it
says:
/wsa:To
This OPTIONAL element (of type xs:anyURI) provides the
value for the [destination] property. If this element is NOT present then
the value of the [destination] property is "http://www.w3.org/2005/03/addressing/role/anonymous".
Otherwise the [children] of this element convey the value of this property.
This applies to all messages.
Some of this is reading between the
lines, but to me the WSA spec was simply
trying to encourage people to use a
real IRI for the wsa:To and trying to find a way
to have a copy of the transprt URL within
the envelope in order to make the envelope
a self-contained/self-describing entity.
There are however cases where a
transport URL is not available (like
on the HTTP response
flow), and these are the cases where
anonymous IRI makes sense.
Since we need a way to deliver ACKs
for one-way messages even when a
firewall is in place I believe using
the anonymous IRI is a valid choice.
w.r.t. your intermediary examining the
wsa:ReplyTo - be a bit careful here.
The presence of a wsa:ReplyTo does not
imply anything about the MEP (sadly :-(.
There are cases where a wsa:ReplyTo
could be present even for a one-way
message. And the presence of an
anonymous wsa:ReplyTo does not guarantee
that anything will flow back on the
http response flow.
thanks,
-Doug
[1] http://www.w3.org/TR/2005/WD-ws-addr-core-20050331/
"Lei Jin" <>
07/11/2005 03:18 PM
To
<>
cc
Subject
[ws-rx] NEW ISSUE: anonymous
AcksTo
I have the impression after talking to a few people
that there is the
implicit assumption (though not specifically called out) in the spec
that if the AcksTo EPR is set to use the anonymous IRI, then all
subsequent acknowledgements for that reliable sequence will be sent back
synchronously on the http response path of either the application
message or an ack request message.
I think that is not a good idea. First of all, we are saying that
even
if my application message is one way (or asynchronous), I might still
receive something back on the http response(the WS-RX ack). Nothing
really precludes this usage, but we are introducing unnecessary
dependency between WS-RX (acknowledgement messages) and WS-Addressing
(normal MEP). For example, if I have an intermediary on the server
side
that takes an incoming message, looks at the reply-to address (or
message MEP), and decides to close http connection if it's a oneway or
asynchronous message, everything works fine. Now, with WS-RX, it
has to
know that "hmm, maybe I shouldn't close that connection if WS-RX is
involved and synchronous ack is used".
Secondly, the paragraph below quoted from WS-Addressing spec says the
anonymous IRI shouldn't be used as the destination in any other
circumstances other than the destination for reply messages. I don't
see acknowledgements as reply messages.
WS-Addressing defines the following well-known IRI for use by endpoints
that cannot have a stable, resolvable IRI:
"http://www.w3.org/2005/03/addressing/role/anonymous" Requests
whose
[reply endpoint], [source endpoint] and/or [fault endpoint] use this
address MUST provide some out-of-band mechanism for delivering replies
or faults (e.g. returning the reply on the same transport connection).
This mechanism may be a simple request/reply transport protocol (e.g.,
HTTP GET or POST). This IRI MAY be used as the [destination] for reply
messages and SHOULD NOT be used as the [destination] in other
circumstances.
Proposal 1:
Specifically call out that the AcksTo EPR should not use the anonymous
IRI.
-- One reason to use an anonymous IRI is so that the acknowledgement may
reach sending endpoints that may be sitting behind a NAT or firewall.
But we have to deal with the same problem with asynchronous response
messages anyway.
Proposal 2:
Specifically call out that an anonymous IRI in the AcksTo EPR would
indicate acknowledgement message will only be sent back in response to
ack request messages where the ack request message should be a
standalone synchronous invoke.
Flames?
Lei
