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Re: Updated Proposal for Rewrite of Part 1 Section 2

From: Marc Hadley <marc.hadley@sun.com>
Date: Mon, 11 Feb 2002 17:38:00 +0000
Message-ID: <3C680178.2040003@sun.com>
To: XML Protocol Discussion <xml-dist-app@w3.org>
CC: David Fallside <fallside@us.ibm.com>
Following a couple of requests, attached is a redlined version showing 
the changes from the orginal SOAPProcessingModelNoActor.htm[1].


[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 Monday, 11 February 2002 12:40:38 UTC

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