NEW issue: WS-C: Make precise, permissive statement relating to methodsof context propagation

[Alastair Green <alastair.green@choreology.com>]

Issue name -- WS-C: Make precise, permissive statement relating to 
methods of context propagation.

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Target document and draft:

Protocol:  Coord

Artifact:  spec

Draft:

Coord spec working draft uploaded 2005-12-02

Link to the document referenced:

http://www.oasis-open.org/committees/download.php/15738/WS-Coordination-2005-11-22.pdf

Section and PDF line number:

Section 2 "Coordination Context", ll. 136-137, ll. 177-178


Issue type:

Editorial (minor)


Related issues:

Issue [] WS-C: Remove fault 4.5 ContextRefused


Issue Description:

Means of context propagation by application cannot be prescribed by WS- 
Coordination.


Issue Details:

ll. 136-137 containt the following sentence:

"CoordinationContext elements are placed within application messages."

ll. 177-178 read:

"When an application propagates an activity using a coordination 
service, applications MUST include a
Coordination context in the outgoing message."

These two statements are examples of how contexts may be communicated, 
flowed or propagated. They are not the only examples. This wording is 
overly prescriptive. It is also a little imprecise.

For example: a context might have a static value, which is well-known, 
and is supplied by publication which
does not even involve computers. Imagine a procurement transaction which 
occurs daily, but reuses the same
static context value. All registered suppliers are provided with a 
context value, which they receive by means
which are out-of-band to the distributed procurement system. The term 
"application message" tends to convey
"network message".

The general statement used elsewhere in the spec (ll. 26-27) is preferable:

"Once a coordination context is acquired by an application, it is then 
sent by whatever appropriate means to
another application."

The second aentence cited above (ll. 177-178) contains a very strong 
(MUST) statement, whose meaning is not
very clear, in several respects.

    * An application does not "propagate an activity using a 
coordination service", it propagates the context
    of an activity, which has been generated by a coordination service. 
The coordination service is not the
    agent of propagation.

    * The term "outgoing message" is not defined. Outgoing from who to 
whom? There may not be an outgoing
    message in a given application protocol.

    * The term "include" is not well-defined. If an interoperability 
spec makes a statement that something
    MUST be done then it usually implies that something predictable will 
happen, either on the wire, or in
    terms of the actions or reactions of an actor in a protocol. Here, 
the most we can say is that the context
    will have to arrive in the hands of a registering service 
(requester) by some means.

The statement immediately following (ll. 179-180), relating to use of 
SOAP headers and the MustUnderstand flag, is precise and necessary.

 
Proposed Resolution:

Replace the paragraph (ll. 135-139), which reads:

"The CoordinationContext is a Context type that is used to pass 
Coordination information to parties
involved in a coordination service. CoordinationContext elements are 
placed within application
messages. Conveying a context on an application message is commonly 
referred to as flowing the
context. A CoordinationContext provides access to a coordination 
registration service, a coordination
type, and relevant extensions."

with the paragraph:

 "The CoordinationContext is used by applications to pass Coordination 
information to parties involved in an
 activity. CoordinationContext elements are propagated to parties which 
may need to register Participants for
 the activity, using application-defined mechanisms -- e.g. as a header 
element of a SOAP application message
 sent to such parties. (Conveying a context in an application message is 
commonly referred to as flowing the
 context.) A CoordinationContext provides access to a coordination 
registration service, a coordination type, and relevant extensions."

Replace the statement (ll. 177-178)

"When an application propagates an activity using a coordination 
service, applications MUST include a
Coordination context in the outgoing message."

with the following sentence:

"An application may propagate a CoordinationContext element as a child 
element of the Body, or of the Header,
of an application SOAP message. [delete new paragraph and run on to next 
sentence]"