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Re: i028: Implications of the presence of ReplyTo

From: Marc Hadley <Marc.Hadley@Sun.COM>
Date: Thu, 11 Nov 2004 14:02:12 -0500
To: Martin Gudgin <mgudgin@microsoft.com>
Cc: public-ws-addressing@w3.org
Message-id: <3219BD29-3414-11D9-B427-000A95BC8D92@Sun.COM>

On Nov 11, 2004, at 7:26 AM, Martin Gudgin wrote:
>> Issue 28[1] concerns the implications of the presence of
>> ReplyTo in a
>> message. Does the presence of a wsa:ReplyTo imply that a reply is
>> required, does absence of ReplyTo indicate a one-way message ?
>>
>> <wsa:ReplyTo> is optional and the specification states that:
>>
>> (i) It "MUST be present if a reply is expected",
>> (ii) But "If the [reply endpoint] is absent, the contents of the
>> [source endpoint] may be used to formulate a message to the source."
>> [reply endpoint] serializes as wsa:ReplyTo, [source endpoint]
>> serializes as wsa:From.
>>
>> I.e. <wsa:ReplyTo> must be present, but if not use <wsa:From>
>> instead -
>> the two statements seem to be contradictory.
>
> I don't think they are. If you expect a reply ( e.g. you're sending the
> initial message a WSDL 1.1 request-response ) then the message you send
> MUST have a [reply endpoint] property. I think the second clause about
> [source endpoint] is just informational, it doesn't have any bearing on
> the previous text. May be it should be under [source endpoint]?
>
So it sounds like you'd be in favor of saying that presence of ReplyTo 
implies a request is expected and that absence indicates a one-way 
message ?

>>
>> If we accept (i) then a typical use of a request response MEP
>> using the
>> SOAP/HTTP binding would require the presence of the following header
>> block:
>>
>> <wsa:ReplyTo>
>>
>> <wsa:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/
>> anonymous</wsa:Address>
>> </wsa:ReplyTo>
>>
>> This is a lot of bytes that provide no real information. My
>> preference
>> would be that omission of a ReplyTo is semantically
>> equivalent to its
>> presence as shown above but that would mean that its presence
>> cannot be
>> used to determine whether a reply is expected or not.
>
> I think providing a 'default' value in the case is a mistake. I saw one
> of the benefits of WS-Addressing was that the headers that appeared in 
> a
> message DID NOT vary depending on how the message was actually
> transmitted.
>
I wasn't suggesting the headers would vary depending on how it was 
transmitted, just that omission would be equivalent to inclusion with 
an anonymous address. However, if we are going to attribute MEP 
semantics to the presence or absence of ReplyTo then I'd modify my 
suggestion to say that omission of a <wsa:Address> be made semantically 
equivalent to inclusion of one using the anonymous URI. I see this as 
similar to the ability to omit the soap:Header if there aren't any soap 
headers in a message and to omit the soap:mustUnderstand instead of 
being forced to put soap:mustUnderstand='false' on a header block.

Marc.

>>
>> [1] http://www.w3.org/2002/ws/addr/wd-issues/#i028
---
Marc Hadley <marc.hadley at sun.com>
Web Technologies and Standards, Sun Microsystems.
Received on Thursday, 11 November 2004 19:02:09 GMT

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