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Re: Updated Proposal for Rewrite of Part 1 Section 2

From: Marc Hadley <marc.hadley@sun.com>
Date: Tue, 12 Feb 2002 11:21:11 +0000
Message-ID: <3C68FAA7.7050800@sun.com>
To: Jacek Kopecky <jacek@systinet.com>
CC: XML Protocol Discussion <xml-dist-app@w3.org>
Jacek Kopecky wrote:

 >  it seems this does not say much about the fact that missing role
 > attribute information item means that the block is targeted at
 > the ultimatereceiver role.
 >  I'm not sure whether this is the intent or not. I thought we
 > wanted to create an ultimatereceiver role URI and make this
 > equivalent to the AII not being present at all.

 From my original message:

 > Note that Part 1, section 4.2.2 currently states: "Omitting the SOAP
 > actor attribute information item implicitly targets the SOAP header
 > block at the ultimate SOAP receiver. An empty value for this attribute
 > is equivalent to omitting the attribute completely, i.e. targeting the
 > block at the ultimate SOAP recipient." This may require a small tweak to
 > say that an ommitted role attribute or a value of "" is equivalent to
 > "http://www.w3.org/2001/12/soap-envelope/role/ultimatereceiver".

I think section 4.2.2 is the right place for this information and that 
there is no need to repeat it in section 2. This is the same approach we 
use for the mU attribute...

Regards,
Marc.

> 
> 
> On Mon, 11 Feb 2002, Marc Hadley wrote:
> 
>  > Following a couple of requests, attached is a redlined version showing 
>  > the changes from the orginal SOAPProcessingModelNoActor.htm[1].
>  >  > Regards,
>  > Marc.
>  >  > [1] http://lists.w3.org/Archives/Public/xml-dist-app/2002Jan/0338.html
>  >  > Marc Hadley wrote:
>  >  > > Following on from the discussion and associated action item from last 
>  > > weeks telcon, please find attached an updated proposal for part 1, 
>  > > section 2. This incorporates comments from Noah and Henrik.
>  > >  > > Note that Part 1, section 4.2.2 currently states: "Omitting the SOAP 
>  > > actor attribute information item implicitly targets the SOAP header 
>  > > block at the ultimate SOAP receiver. An empty value for this attribute 
>  > > is equivalent to omitting the attribute completely, i.e. targeting the 
>  > > block at the ultimate SOAP recipient." This may require a small tweak to 
>  > > say that an ommitted role attribute or a value of "" is equivalent to 
>  > > "http://www.w3.org/2001/12/soap-envelope/role/ultimatereceiver".
>  > >  > > Regards,
>  > > Marc.
>  > >  > >  > > ------------------------------------------------------------------------
>  > >  > >  > >     2 SOAP Processing Model
>  > >  > > SOAP messages are fundamentally one-way transmissions from a SOAP sender 
>  > > to a SOAP receiver; however, SOAP messages are often combined to 
>  > > implement patterns such as request/response.
>  > >  > > SOAP implementations can be optimized to exploit the unique 
>  > > characteristics of particular network systems. For example, the HTTP 
>  > > binding described in [1] <#SOAP-PART2>(SOAP in HTTP 
>  > > <..\..\..\..\..\Documents%20and%20Settings\MartinG\Local%20Settings\Temporary%20Internet%20Files\Content.IE5\41YRS1MJ\soap12-part2.html#soapinhttp>) 
>  > > provides a request/response message exchange pattern that may be 
>  > > leveraged by SOAP applications.
>  > >  > > SOAP provides a distributed processing model that assumes that a SOAP 
>  > > message originates at an initial SOAP sender and is sent to an ultimate 
>  > > SOAP receiver via zero or more SOAP intermediaries. This section defines 
>  > > the SOAP distributed processing model. Section 5 defines a framework for 
>  > > describing how additional features such as routing, reliability and 
>  > > security fit into the distributed processing model.
>  > >  > >  > >       2.1 SOAP Nodes
>  > >  > > A SOAP node can be the initial SOAP sender, the ultimate SOAP receiver, 
>  > > or a SOAP intermediary, in which case it is both a SOAP sender and a 
>  > > SOAP receiver.
>  > >  > > A SOAP node receiving a SOAP message MUST perform processing according 
>  > > to the SOAP processing model as described in this section and by the 
>  > > remainder of this specification.
>  > >  > >  > >       2.2 SOAP Roles and SOAP Nodes
>  > >  > > In processing a SOAP message, a SOAP node is said to act in one or more 
>  > > SOAP roles, each of which is identified by a URI known as the SOAP role 
>  > > name. The roles assumed MUST be invariant during the processing of an 
>  > > individual SOAP message; because this specification deals only with the 
>  > > processing of individual SOAP messages, no statement is made regarding 
>  > > the possibility that a given piece of software might or might not act in 
>  > > varying roles when processing more than one SOAP message.
>  > >  > > The following roles are defined by this specification:
>  > >  > > "http://www.w3.org/2001/12/soap-envelope/role/next" Each SOAP node MUST 
>  > > act in this role and can additionally assume zero or more other SOAP roles.
>  > >  > > "http://www.w3.org/2001/12/soap-envelope/role/none" SOAP nodes MUST NOT 
>  > > act in this role.
>  > >  > > "http://www.w3.org/2001/12/soap-envelope/role/ultimatereceiver" To 
>  > > establish itself as the as the ultimate SOAP receiver a SOAP node MUST 
>  > > act in this role. SOAP intermediaries MUST NOT act in this role.
>  > >  > > While the purpose of a SOAP role name is to identify a SOAP node, there 
>  > > are no routing or message exchange semantics associated with the SOAP 
>  > > role name. For example, SOAP roles MAY be named with a URI useable to 
>  > > route SOAP messages to an appropriate SOAP node. Conversely, it is also 
>  > > appropriate to use SOAP roles with names that are related more 
>  > > indirectly to message routing (e.g. 
>  > > "http://example.org/banking/anyAccountMgr") or which are unrelated to 
>  > > routing (e.g. a URI meant to identify "all cache management software"; 
>  > > such a header might be used, for example, to carry an indication to any 
>  > > concerned software that the containing SOAP message is idempotent, and 
>  > > can safely be cached and replayed.)
>  > >  > > Except for "http://www.w3.org/2001/12/soap-envelope/role/next", 
>  > > "http://www.w3.org/2001/12/soap-envelope/role/none" and 
>  > > "http://www.w3.org/2001/12/soap-envelope/role/ultimatereceiver" this 
>  > > specification does not prescribe the criteria by which a given node 
>  > > determines the set of roles in which it acts on a given message. For 
>  > > example, implementations can base this determination on factors 
>  > > including, but not limited to: hardcoded choices in the implementation, 
>  > > information provided by the transport binding (e.g. the URI to which the 
>  > > message was physically delivered), configuration information made by 
>  > > users during system installation, etc.
>  > >  > >  > >       2.3 Targeting SOAP Header Blocks
>  > >  > > SOAP header blocks carry optional role attribute information items (see 
>  > > 4.2.2 SOAP role Attribute <#soapactor>) that are used to target them to 
>  > > the appropriate SOAP node(s). This specification refers to the (implicit 
>  > > or explicit) value of the SOAP role attribute as the SOAP role for the 
>  > > corresponding SOAP header block.
>  > >  > > A SOAP header block is said to be targeted to a SOAP node if the SOAP 
>  > > role for the header block matches a role played by the SOAP node.
>  > >  > > Header blocks targeted to the special role 
>  > > "http://www.w3.org/2001/12/soap-envelope/role/none" are carried with the 
>  > > message to the ultimate receiver, but are never formally "processed". 
>  > > Such blocks MAY carry data that is required for processing of other blocks.
>  > >  > > The ultimate SOAP recipient of a SOAP message is additionally 
>  > > responsible for processing the message body. The SOAP message path for 
>  > > that message ends at the ultimate recipient.
>  > >  > >  > >       2.4 Understanding SOAP Headers
>  > >  > > It is likely that specifications for a wide variety of header functions 
>  > > will be developed over time, and that some SOAP nodes MAY include the 
>  > > software necessary to implement one or more such extensions. A SOAP 
>  > > header block is said to be understood by a SOAP node if the software at 
>  > > that SOAP node has been written to fully conform to and implement the 
>  > > semantics conveyed by the combination of local name and namespace name 
>  > > of the outer-most element information item of that SOAP header block.
>  > >  > > SOAP header blocks carry optional mustUnderstand attribute information 
>  > > items (see 4.2.3 SOAP mustUnderstand Attribute <#soapmu>). When the 
>  > > value of such an attribute information item is logically ?True?, the 
>  > > SOAP block is said to be mandatory.
>  > >  > > For every mandatory SOAP header block targeted to a node, that node MUST 
>  > > either process the block or not process the SOAP message at all, and 
>  > > instead generate a fault (see 2.6 Processing SOAP Messages 
>  > > <#procsoapmsgs> and 4.4 SOAP Fault <#soapfault>).
>  > >  > > Mandatory blocks MUST be presumed to somehow modify the semantics of 
>  > > other headers or body elements. Tagging SOAP blocks as mandatory thus 
>  > > assures that such changes in semantics will not be silently (and, 
>  > > presumably, erroneously) ignored by a SOAP node to which the header 
>  > > block is targetted.
>  > >  > > The mustUnderstand attribute information item is not intended as a 
>  > > mechanism for detecting errors in routing, misidentification of nodes, 
>  > > failure of a node to serve in its intended role(s), etc., any of which 
>  > > may result in a failure to even attempt processing of a given SOAP 
>  > > header block from a SOAP envelope. This specification therefore does not 
>  > > require any fault to be generated based on the presence or value of this 
>  > > attribute on a SOAP header block not targeted at the current processing 
>  > > node, for example when it is suspected that such a block has survived 
>  > > erronously due to a routing or targeting error at a preceeding 
>  > > intermediairy. In particular, it is not an error for a mandatory header 
>  > > block targeted to a role other than the ones assumed by the ultimate 
>  > > SOAP receiver to reach that node without having been processed.
>  > >  > >  > >       2.5 Structure and Interpretation of SOAP Bodies
>  > >  > > A SOAP body consists of zero or more namespace qualified element 
>  > > information items, which are the immediate children of the Body element 
>  > > information item. The ultimate SOAP receiver MUST correctly process all 
>  > > such body elements. However, Part 1 of this specification (this 
>  > > document) mandates no particular structure or interpretation of such 
>  > > elements, and provides no standard means for specifying the processing 
>  > > to be done.
>  > >  > >  > >       2.6 Processing SOAP Messages
>  > >  > > This section sets out the rules by which SOAP messages are processed. 
>  > > Unless otherwise stated, processing must be semantically equivalent to 
>  > > performing the following steps separately, and in the order given. Note 
>  > > however that nothing in this specification should be taken to prevent 
>  > > the use of optimistic concurrency, roll back, or other techniques that 
>  > > might provide increased flexibility in processing order as long as all 
>  > > SOAP messages, SOAP faults and application-level side effects are 
>  > > equivalent to those that would be obtained by direct implementation of 
>  > > the following rules in the order shown below.
>  > >  > > 1.      Determine the set of roles in which the node is to act. The 
>  > > contents of the SOAP envelope, including header blocks and the body, MAY 
>  > > be inspected in making such determination.
>  > >  > > 2.      Identify all header blocks targeted at the node that are mandatory.
>  > >  > > 3.      If one or more of the header blocks identified in the preceding 
>  > > step are not understood by the node then generate a single SOAP 
>  > > MustUnderstand fault (see 4.4.6 MustUnderstand Faults <#mufault>). If 
>  > > such a fault is generated, any further processing MUST NOT be done.
>  > >  > > 4.      Process all header blocks targeted at the node and, in the case 
>  > > of the ultimate SOAP recipient, the SOAP body. A SOAP node MUST process 
>  > > all SOAP header blocks targeted at it. A SOAP node MAY choose to ignore 
>  > > the processing implied by non-mandatory SOAP header blocks targeted at it.
>  > >  > > 5.      In the case of a SOAP intermediary, where the message is to be 
>  > > forwarded further along the message path, remove all SOAP header blocks 
>  > > targeted at the node, and possibly insert new SOAP header blocks.
>  > >  > > In all cases where a SOAP header block is processed, the SOAP node must 
>  > > understand the SOAP header block and must do such processing in a manner 
>  > > fully conformant with the specification for that block. The ultimate 
>  > > recipient MUST process the SOAP body, in a manner consistent with 2.5 
>  > > Structure and Interpretation of SOAP Bodies <#structinterpbodies>.
>  > >  > > If processing is unsuccessful, exactly one fault MUST be generated by 
>  > > the node. Header-related faults other than mustUnderstand faults (see 
>  > > 4.4 SOAP Fault <#soapfault>) MUST be SOAP Sender or DataEncodingUnknown 
>  > > faults (see 4.4.5 SOAP Fault Codes <#faultcodes>) and MUST conform to 
>  > > the specification for the corresponding SOAP header block. Faults 
>  > > relating to the body MUST be SOAP Sender or DataEncodingUnknown faults 
>  > > (see 4.4.5 SOAP Fault Codes <#faultcodes>).
>  > >  > > SOAP nodes can make reference to any information in the SOAP envelope 
>  > > when processing a SOAP block. For example, a caching function can cache 
>  > > the entire SOAP message, if desired.
>  > >  > > The processing of particular SOAP header block MAY control or determine 
>  > > the order of processing for other SOAP header blocks and/or the SOAP 
>  > > body. For example, one could create a SOAP header block to force 
>  > > processing of other SOAP header blocks in lexical order. In the absence 
>  > > of such a controlling block, the order of header and body processing is 
>  > > at the discretion of the SOAP node; header blocks MAY be processed in 
>  > > arbitrary order, and such processing MAY precede, be interleaved with, 
>  > > or MAY follow processing of the body. For example, a "begin transaction" 
>  > > header block would typically precede, a "commit transaction" would 
>  > > likely follow, and a "logging" function might run concurrently with body 
>  > > processing.
>  > >  > > If the SOAP node is a SOAP intermediary, the SOAP message pattern and 
>  > > results of processing (e.g. no fault generated) MAY require that the 
>  > > SOAP message be sent further along the SOAP message path. Such relayed 
>  > > SOAP messages MUST contain all SOAP header blocks and the SOAP body from 
>  > > the original SOAP message, in the original order, except that SOAP 
>  > > header blocks targeted at the SOAP intermediary MUST be removed (such 
>  > > SOAP blocks are removed regardless of whether they were processed or 
>  > > ignored). Additional SOAP header blocks MAY be inserted at any point in 
>  > > the SOAP message, and such inserted SOAP header blocks MAY be 
>  > > indistinguishable from one or more just removed (effectively leaving 
>  > > them in place, but emphasizing the need to reinterpret at each SOAP node 
>  > > along the SOAP message path.)
>  > >  > > Note:
>  > >  > > The above rules apply to processing at a single node. SOAP features MAY 
>  > > be designed to ensure that mandatory (and other) headers are processed 
>  > > in an appropriate order, as the message moves along the message path 
>  > > towards the ultimate recipient. Specifically, such extensions might 
>  > > specify that a (Sender) fault is generated if some SOAP header blocks 
>  > > have inadvertently survied past some intended point in the message path. 
>  > > Such features MAY depend on the presence or value of the mustUnderstand 
>  > > attribute information item in the surviving headers when determining 
>  > > whether an error has occurred.
>  > >  > >   > >  >  >  > 
> 


-- 
Marc Hadley <marc.hadley@sun.com>
XML Technology Centre, Sun Microsystems.
Received on Tuesday, 12 February 2002 06:21:17 GMT

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