Web Services Reliable Messaging (WS-ReliableMessaging)
Web
Services Reliable Messaging (WS-ReliableMessaging)
Committee Draft 04, August 11, 2006
wsrm-1.1-spec-cd-04
http://docs.oasis-open.org/ws-rx/wsrm/200608/wsrm-1.1-spec-cd-04.pdf
See the Acknowledgments (Appendix E).
This specification (WS-ReliableMessaging) describes a protocol that allows messages to be transferred reliably between nodes implementing this protocol in the presence of software component, system, or network failures. The protocol is described in this specification in a transport-independent manner allowing it to be implemented using different network technologies. To support interoperable Web services, a SOAP binding is defined within this specification.
The protocol defined in this specification depends upon other Web services specifications for the identification of service endpoint addresses and policies. How these are identified and retrieved are detailed within those specifications and are out of scope for this document.
By using the XML [XML], SOAP [SOAP 1.1], [SOAP 1.2] and WSDL [WSDL 1.1] extensibility model, SOAP-based and WSDL-based specifications are designed to be composed with each other to define a rich Web services environment. As such, WS-ReliableMessaging by itself does not define all the features required for a complete messaging solution. WS-ReliableMessaging is a building block that is used in conjunction with other specifications and application-specific protocols to accommodate a wide variety of requirements and scenarios related to the operation of distributed Web services.
This document was last revised or approved by the WS-RX on the above date. The level of approval is also listed above. Check the current location noted above for possible later revisions of this document. This document is updated periodically on no particular schedule. Technical Committee members should send comments on this specification to the Technical Committee's email list. Others should send comments to the Technical Committee by using the "Send A Comment" button on the Technical Committee's web page at http://www.oasis-open.org/committees/ws-rx. For information on whether any patents have been disclosed that may be essential to implementing this specification, and any offers of patent licensing terms, please refer to the Intellectual Property Rights section of the Technical Committee web page (http://www.oasis-open.org/committees/ws-rx/ipr.php). The non-normative errata page for this specification is located at http://www.oasis-open.org/committees/ws-rx.
1.2 Namespace
1.3 Compliance
2.1 Glossary
3.1 Considerations on the Use of Extensibility Points
3.2 Considerations on the Use of "Piggy-Backing"
3.3 Composition with WS-Addressing
3.7 Sequences
3.10 MakeConnection
3.11 MessagePending
4 Faults
4.3 Unknown Sequence
4.7 Sequence Closed
4.8 WSRM Required
5 Security Threats and Countermeasures
5.1 Threats and Countermeasures
5.1.1 Integrity Threats
5.1.1.1 Countermeasures
5.1.2 Resource Consumption Threats
5.1.2.1 Countermeasures
5.1.3 Sequence Spoofing Threats
5.1.3.1 Sequence Hijacking
5.1.3.2 Countermeasures
5.2 Security Solutions and Technologies
5.2.1 Transport Layer Security
5.2.1.1 Model
5.2.1.2 Countermeasure Implementation
5.2.2 SOAP Message Security
5.2.2.1 Model
5.2.2.2 Countermeasure Implementation
7.1 Normative
7.2 Non-Normative
Appendix A. Schema
Appendix B. WSDL
Appendix C. Message Examples
Appendix C.1 Create Sequence
Appendix C.2 Initial Transmission
Appendix C.3 First Acknowledgement
Appendix C.4 Retransmission
Appendix C.5 Termination
Appendix C.6 MakeConnection
Appendix D. State Tables
Appendix E. Acknowledgments
Appendix F. Revision History
Appendix G. Notices
It is often a requirement for two Web services that wish to communicate to do so reliably in the presence of software component, system, or network failures. The primary goal of this specification is to create a modular mechanism for reliable transfer of messages. It defines a messaging protocol to identify, track, and manage the reliable transfer of messages between a source and a destination. It also defines a SOAP binding that is required for interoperability. Additional bindings can be defined.
This mechanism is extensible allowing additional functionality, such as security, to be tightly integrated. This specification integrates with and complements the WS-Security [WS-Security], WS-Policy [WS-Policy], and other Web services specifications. Combined, these allow for a broad range of reliable, secure messaging options.
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [KEYWORDS].
This specification uses the following syntax to define normative outlines for messages:
The syntax appears as an XML instance, but values in italics indicate data types instead of values.
Characters are appended to elements and attributes to indicate cardinality:
"?" (0 or 1)
"*" (0 or more)
"+" (1 or more)
The character "|" is used to indicate a choice between alternatives.
The characters "[" and "]" are used to indicate that contained items are to be treated as a group with respect to cardinality or choice.
An ellipsis (i.e. "...") indicates a point of extensibility that allows other child or attribute content specified in this document. Additional children elements and/or attributes MAY be added at the indicated extension points but they MUST NOT contradict the semantics of the parent and/or owner, respectively. If an extension is not recognized it SHOULD be ignored.
XML namespace prefixes (See Section 1.2) are used to indicate the namespace of the element being defined.
Elements and Attributes defined by this specification are referred to in the text of this document using XPath 1.0 [XPATH 1.0] expressions. Extensibility points are referred to using an extended version of this syntax:
An element extensibility point is referred to using {any} in place of the element name. This indicates that any element name can be used, from any namespace other than the wsrm: namespace.
An attribute extensibility point is referred to using @{any} in place of the attribute name. This indicates that any attribute name can be used, from any namespace other than the wsrm: namespace.
The XML namespace [XML-ns] URI that MUST be used by implementations of this specification is:
Dereferencing the above URI will produce the Resource Directory Description Language [RDDL 2.0] document that describes this namespace.
Table 1 lists the XML namespaces that are used in this specification. The choice of any namespace prefix is arbitrary and not semantically significant.
Table 1
|
Prefix |
Namespace |
|---|---|
|
S |
(Either SOAP 1.1 or 1.2) |
|
S11 |
http://schemas.xmlsoap.org/soap/envelope/ |
|
S12 |
http://www.w3.org/2003/05/soap-envelope |
|
wsrm |
http://docs.oasis-open.org/ws-rx/wsrm/200608 |
|
wsa |
http://www.w3.org/2005/08/addressing |
|
wsaw |
http://www.w3.org/2006/05/addressing/wsdl |
|
wsse |
http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd |
|
xs |
http://www.w3.org/2001/XMLSchema |
The normative schema for WS-ReliableMessaging can be found linked from the namespace document that is located at the namespace URI specified above.
All sections explicitly noted as examples are informational and are not to be considered normative.
An implementation is not compliant with this specification if it fails to satisfy one or more of the MUST or REQUIRED level requirements defined herein. A SOAP Node MUST NOT use the XML namespace identifier for this specification (listed in Section 1.2) within SOAP Envelopes unless it is compliant with this specification.
Normative text within this specification takes precedence over normative outlines, which in turn take precedence over the XML Schema [XML Schema Part 1, Part 2] descriptions.
Many errors can interrupt a conversation. Messages can be lost, duplicated or reordered. Further the host systems can experience failures and lose volatile state.
The WS-ReliableMessaging specification defines an interoperable protocol that enables a Reliable Messaging (RM) Source to accurately determine the disposition of each message it Transmits as perceived by the RM Destination, so as to allow it to resolve any in-doubt status regarding receipt of the message Transmitted. The protocol also enables an RM Destination to efficiently determine which of those messages it Receives have been previously Received, enabling it to filter out duplicate message transmissions caused by the retransmission, by the RM Source, of unacknowledged message. It also enables an RM Destination to Deliver the messages it Receives to the Application Destination in the order in which they were sent by an Application Source, in the event that they are Received out of order. Note that this specification places no restriction on the scope of the RM Source or RM Destination entities. For example, either can span multiple WSDL Ports or Endpoints.
The protocol enables the implementation of a broad range of reliability features which include ordered Delivery, duplicate elimination, and guaranteed receipt. The protocol can also be implemented with a range of robustness characteristics ranging from in-memory persistence that is scoped to a single process lifetime, to replicated durable storage that is recoverable in all but the most extreme circumstances. It is expected that the Endpoints will implement as many or as few of these reliability characteristics as necessary for the correct operation of the application using the protocol. Regardless of which of the reliability features is enabled, the wire protocol does not change.
Figure 1 below illustrates the entities and events in a simple reliable exchange of messages. First, the Application Source Sends a message for reliable transfer. The Reliable Messaging Source accepts the message and Transmits it one or more times. After accepting the message, the RM Destination Acknowledges it. Finally, the RM Destination Delivers the message to the Application Destination. The exact roles the entities play and the complete meaning of the events will be defined throughout this specification.
Figure 1: Reliable Messaging Model
The following definitions are used throughout this specification:
Accept: The act of qualifying a message by the RM Destination such that it becomes eligible for Delivery and acknowledgement.
Acknowledgement: The communication from the RM Destination to the RM Source indicating the successful receipt of a message.
Acknowledgement Message: A message containing a SequenceAcknowledgement header block. Acknowledgement Messages may or may not contain a SOAP body.
Acknowledgement Request: A message containing a AckRequested header. Acknowledgement Requests may or may not contain a SOAP body.
Application Destination: The Endpoint to which a message is Delivered.
Application Source: The Endpoint that Sends a message.
Deliver: The act of transferring a message from the RM Destination to the Application Destination.
Endpoint: As defined in the WS-Addressing specification [WS-Addressing]; a Web service Endpoint is a (referenceable) entity, processor, or resource to which Web service messages can be addressed. Endpoint references convey the information needed to address a Web service Endpoint.
Receive: The act of reading a message from a network connection and accepting it.
RM Destination: The Endpoint that Receives messages Transmitted reliably from an RM Source.
RM Protocol Header Block: One of Sequence, SequenceAcknowledgement, or AckRequested.
RM Source: The Endpoint that Transmits messages reliably to an RM Destination.
Send: The act of transferring a message from the Application Source to the RM Source for reliable transfer.
Sequence Lifecycle Message: A message that contains one of: CreateSequence, CreateSequenceResponse, CloseSequence, CloseSequenceResponse, TerminateSequence, TerminateSequenceResponse as the child element of the SOAP body element.
Sequence Traffic Messsage: A message containing a Sequence header block.
Transmit: The act of writing a message to a network connection.
The correct operation of the protocol requires that a number of preconditions MUST be established prior to the processing of the initial sequenced message:
For any single message exchange the RM Source MUST have an endpoint reference that uniquely identifies the RM Destination Endpoint.
The RM Source MUST have successfully created a Sequence with the RM Destination.
The RM Source MUST be capable of formulating messages that adhere to the RM Destination's policies.
If a secure exchange of messages is REQUIRED, then the RM Source and RM Destination MUST have a security context.
During the lifetime of a Sequence, two invariants are REQUIRED for correctness:
The RM Source MUST assign each message within a Sequence a message number (defined below) beginning at 1 and increasing by exactly 1 for each subsequent message. These numbers MUST be assigned in the same order in which messages are sent by the Application Source.
Within every Acknowledgement Message it issues, the RM Destination MUST include one or more AcknowledgementRange child elements that contain, in their collective ranges, the message number of every message accepted by the RM Destination. The RM Destination MUST exclude, in the AcknowledgementRange elements, the message numbers of any messages it has not accepted.
Figure 2 illustrates a possible message exchange between two reliable messaging Endpoints A and B.
The protocol preconditions are established. These include policy exchange, endpoint resolution, and establishing trust.
The RM Source requests creation of a new Sequence.
The RM Destination creates a new Sequence and returns its unique identifier.
The RM Source begins Transmitting messages in the Sequence beginning with MessageNumber 1. In the figure above, the RM Source sends 3 messages in the Sequence.
The 2nd message in the Sequence is lost in transit.
The 3rd message is the last in this Sequence and the RM Source includes an AckRequested header to ensure that it gets a timely SequenceAcknowledgement for the Sequence.
The RM Destination acknowledges receipt of message numbers 1 and 3 as a result of receiving the RM Source's AckRequested header.
The RM Source retransmits the unacknowledged message with MessageNumber 2. This is a new message from the perspective of the underlying transport, but it has the same Sequence Identifier and MessageNumber so the RM Destination can recognize it as a duplicate of the earlier message, in case the original and retransmitted messages are both Received. The RM Source includes an AckRequested header in the retransmitted message so the RM Destination will expedite an acknowledgement.
The RM Destination Receives the second transmission of the message with MessageNumber 2 and acknowledges receipt of message numbers 1, 2, and 3.
The RM Source Receives this Acknowledgement and sends a TerminateSequence message to the RM Destination indicating that the Sequence is completed and reclaims any resources associated with the Sequence.
The RM Destination Receives the TerminateSequence message indicating that the RM Source will not be sending any more messages. The RM Destination sends a TerminateSequenceResponse message to the RM Source and and reclaims any resources associated with the Sequence.
The RM Source will expect to Receive Acknowledgements from the RM Destination during the course of a message exchange at occasions described in Section 3 below. Should an Acknowledgement not be Received in a timely fashion, the RM Source MUST re-transmit the message since either the message or the associated Acknowledgement might have been lost. Since the nature and dynamic characteristics of the underlying transport and potential intermediaries are unknown in the general case, the timing of re-transmissions cannot be specified. Additionally, over-aggressive re-transmissions have been demonstrated to cause transport or intermediary flooding which are counterproductive to the intention of providing a reliable exchange of messages. Consequently, implementers are encouraged to utilize adaptive mechanisms that dynamically adjust re-transmission time and the back-off intervals that are appropriate to the nature of the transports and intermediaries envisioned. For the case of TCP/IP transports, a mechanism similar to that described as RTTM in RFC 1323 [RTTM] SHOULD be considered.
Now that the basic model has been outlined, the details of the elements used in this protocol are now provided in Section 3.
The following sub-sections define the various RM protocol elements, and prescribe their usage by a conformant implementations.
The following protocol elements define extensibility points at various places. Implementations MAY add child elements and/or attributes at the indicated extension points but MUST NOT contradict the semantics of the parent and/or owner, respectively. If a receiver does not recognize an extension, the receiver SHOULD ignore the extension.
Some RM header blocks may be added to messages that happen to be targeted to the same Endpoint to which those headers are to be sent (a concept often referred to as "piggy-backing"), thus saving the overhead of an additional message exchange. Reference parameters MUST be considered when determining whether two EPRs are targeted to the same Endpoint.
When the RM protocol, defined in this specification, is composed with the WS-Addressing specification, the following rules prescribe the constraints on the value of the wsa:Action header:
When an Endpoint generates a message that carries an RM protocol element, that is defined in section 3 below, in the body of a SOAP envelope that Endpoint MUST include in that envelope a wsa:Action SOAP header block whose value is an IRI that is a concatenation of the WS-RM namespace URI, followed by a "/", followed by the value of the local name of the child element of the SOAP body . For example, for a Sequence creation request message as described in section 3.1 below, the value of the wsa:Action IRI would be:
http://docs.oasis-open.org/ws-rx/wsrm/200608/CreateSequence
When an Endpoint generates an Acknowledgement Message that has no element content in the SOAP body, then the value of the wsa:Action IRI MUST be:
http://docs.oasis-open.org/ws-rx/wsrm/200608/SequenceAcknowledgement
When an Endpoint generates an Acknowledgement Request that has no element content in the SOAP body, then the value of the wsa:Action IRI MUST be:
http://docs.oasis-open.org/ws-rx/wsrm/200608/AckRequested
When an Endpoint generates an RM fault as defined in section 4 below, the value of the wsa:Action IRI MUST be as defined in section 4 below.
The RM Source MUST request creation of an outbound Sequence by sending a CreateSequence element in the body of a message to the RM Destination which in turn responds either with a message containing CreateSequenceResponse or a CreateSequenceRefused fault. The RM Source MAY include an offer to create an inbound Sequence within the CreateSequence message. This offer is either accepted or rejected by the RM Destination in the CreateSequenceResponse message.
The SOAP version used for the CreateSequence message SHOULD be used for all subsequent messages in or for that Sequence, sent by either the RM Source or the RM Destination.
The following exemplar defines the CreateSequence syntax:
<wsrm:CreateSequence ...>
<wsrm:AcksTo> wsa:EndpointReferenceType </wsrm:AcksTo>
<wsrm:Expires ...> xs:duration </wsrm:Expires> ?
<wsrm:Offer ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
<wsrm:Endpoint> wsa:EndpointReferenceType </wsrm:Endpoint>
<wsrm:Expires ...> xs:duration </wsrm:Expires> ?
<wsrm:IncompleteSequenceBehavior>
wsrm:IncompleteSequenceBehaviorType
</wsrm:IncompleteSequenceBehavior> ?
...
</wsrm:Offer> ?
...
</wsrm:CreateSequence>
This element requests creation of a new Sequence between the RM Source that sends it, and the RM Destination to which it is sent. The RM Source MUST NOT send this element as a header block. The RM Destination MUST respond either with a CreateSequenceResponse response message or a CreateSequenceRefused fault.
/wsrm:CreateSequence/wsrm:AcksTo
The RM Source MUST include this element in any CreateSequence message it sends. This element is of type wsa:EndpointReferenceType (as specified by WS-Addressing). It specifies the endpoint reference to which messages containing SequenceAcknowledgement header blocks and faults related to the created Sequence are to be sent, unless otherwise noted in this specification (for example, see Section 3.2).
Implementations MUST NOT use an endpoint reference in the AcksTo element that would prevent the sending of Sequence Acknowledgements back to the RM Source. For example, using the WS-Addressing "http://www.w3.org/2005/08/addressing/none" IRI would make it impossible for the RM Destination to ever send Sequence Acknowledgements.
This element, if present, of type xs:duration specifies the RM Source's requested duration for the Sequence. The RM Destination MAY either accept the requested duration or assign a lesser value of its choosing. A value of "PT0S" indicates that the Sequence will never expire. Absence of the element indicates an implied value of "PT0S".
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
/wsrm:CreateSequence/wsrm:Offer
This element, if present, enables an RM Source to offer a corresponding Sequence for the reliable exchange of messages Transmitted from RM Destination to RM Source.
/wsrm:CreateSequence/wsrm:Offer/wsrm:Identifier
The RM Source MUST set the value of this element to an absolute URI (conformant with RFC3986 [URI]) that uniquely identifies the offered Sequence.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
An RM Source MUST include this element, of type wsa:EndpointReferenceType (as specified by WS-Addressing). This element specifies the endpoint reference to which Sequence Lifecycle Messages, Sequence Traffic Messages, Acknowledgement Requests, and fault messages related to the offered Sequence are to be sent.
Implementations MUST NOT use an endpoint reference in the Endpoint element that would prevent the sending of Sequence Lifecycle Message, Sequence Traffic Message, etc. For example, using the WS-Addressing "http://www.w3.org/2005/08/addressing/none" IRI would make it impossible for the RM Destination to ever send Sequence Lifecycle Messages (e.g. TerminateSequence) to the RM Source for the Offered Sequence. Implementations MAY use the WS-RM anonymous URI template and doing so implies that messages will be retrieved using a mechanism such as the MakeConnection message (see section 3.7).
This element, if present, of type xs:duration specifies the duration for the offered Sequence. A value of "PT0S" indicates that the offered Sequence will never expire. Absence of the element indicates an implied value of "PT0S".
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This element, if present, specifies the behavior that the destination will exhibit upon the closure or termination of an incomplete Sequence. For the purposes of defining the values used, the term "discard" refers to behavior equivalent to the Application Destination never processing a particular message.
A value of “DiscardEntireSequence” indicates that the entire Sequence MUST be discarded if the Sequence is closed, or terminated, when there are one or more gaps in the final SequenceAcknowledgement.
A value of “DiscardFollowingFirstGap” indicates that messages in the Sequence beyond the first gap MUST be discarded when there are one or more gaps in the final SequenceAcknowledgement.
The default value of “NoDiscard” indicates that no acknowledged messages in the Sequence will be discarded.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
A CreateSequenceResponse is sent in the body of a response message by an RM Destination in response to receipt of a CreateSequence request message. It carries the Identifier of the created Sequence and indicates that the RM Source can begin sending messages in the context of the identified Sequence.
The following exemplar defines the CreateSequenceResponse syntax:
<wsrm:CreateSequenceResponse ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
<wsrm:Expires ...> xs:duration </wsrm:Expires> ?
<wsrm:IncompleteSequenceBehavior>
wsrm:IncompleteSequenceBehaviorType
</wsrm:IncompleteSequenceBehavior> ?
<wsrm:Accept ...>
<wsrm:AcksTo> wsa:EndpointReferenceType </wsrm:AcksTo>
...
</wsrm:Accept> ?
...
</wsrm:CreateSequenceResponse>
This element is sent in the body of the response message in response to a CreateSequence request message. It indicates that the RM Destination has created a new Sequence at the request of the RM Source. The RM Destination MUST NOT send this element as a header block.
The RM Destination MUST include this element within any CreateSequenceResponse message it sends. The RM Destination MUST set the value of this element to the absolute URI (conformant with RFC3986) that uniquely identifies the Sequence that has been created by the RM Destination.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This element, if present, of type xs:duration accepts or refines the RM Source's requested duration for the Sequence. It specifies the amount of time after which any resources associated with the Sequence SHOULD be reclaimed thus causing the Sequence to be silently teriminated. At the RM Destination this duration is measured from a point proximate to Sequence creation and at the RM Source this duration is measured from a point approximate to the successful processing of the CreateSequenceResponse. A value of "PT0S" indicates that the Sequence will never expire. Absence of the element indicates an implied value of "PT0S". The RM Destination MUST set the value of this element to be equal to or less than the value requested by the RM Source in the corresponding CreateSequence message.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This element, if present, specifies the behavior that the destination will exhibit upon the closure or termination of an incomplete Sequence. For the purposes of defining the values used, the term "discard" refers to behavior equivalent to the Application Destination never processing a particular message.
A value of “DiscardEntireSequence” indicates that the entire Sequence MUST be discarded if the Sequence is closed, or terminated, when there are one or more gaps in the final SequenceAcknowledgement.
A value of “DiscardFollowingFirstGap” indicates that messages in the Sequence beyond the first gap MUST be discarded when there are one or more gaps in the final SequenceAcknowledgement.
The default value of “NoDiscard” indicates that no acknowledged messages in the Sequence will be discarded.
This element, if present, enables an RM Destination to accept the offer of a corresponding Sequence for the reliable exchange of messages Transmitted from RM Destination to RM Source.
Note: If a CreateSequenceResponse is returned without a child Accept in response to a CreateSequence that did contain a child Offer, then the RM Source MAY immediately reclaim any resources associated with the unused offered Sequence.
The RM Destination MUST include this element, of type wsa:EndpointReferenceType (as specified by WS-Addressing). It specifies the endpoint reference to which messages containing SequenceAcknowledgement header blocks and faults related to the created Sequence are to be sent, unless otherwise noted in this specification (for example, see Section 3.2).
Implementations MUST NOT use an endpoint reference in the AcksTo element that would prevent the sending of Sequence Acknowledgements back to the RM Source. For example, using the WS-Addressing "http://www.w3.org/2005/08/addressing/none" IRI would make it impossible for the RM Destination to ever send Sequence Acknowledgements.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
There are times during the use of an RM Sequence that the RM Source or RM Destination will wish to discontinue using a Sequence. Simply terminating the Sequence discards the state managed by the RM Destination, leaving the RM Source unaware of the final ranges of messages that were successfully transferred to the RM Destination. To ensure that the Sequence ends with a known final state either the RM Source or RM Destination MAY choose to close the Sequence before terminating it.
If the RM Source wishes to close the Sequence, then it sends a CloseSequence element, in the body of a message, to the RM Destination. This message indicates that the RM Destination MUST NOT accept any new messages for the specified Sequence, other than those already accepted at the time the CloseSequence element is interpreted by the RM Destination. Upon receipt of this message, or subsequent to the RM Destination closing the Sequence of its own volition, the RM Destination MUST include a final SequenceAcknowledgement (within which the RM Destination MUST include the Final element) header block on any messages associated with the Sequence destined to the RM Source, including the CloseSequenceResponse message or on any Sequence fault Transmitted to the RM Source.
While the RM Destination MUST NOT accept any new messages for the specified Sequence it MUST still process Sequence Lifecyle Messages and Acknowledgement Requests. For example, it MUST respond to AckRequested, TerminateSequence as well as CloseSequence messages. Note, subsequent CloseSequence messages have no effect on the state of the Sequence.
In the case where the RM Destination wishes to discontinue use of a Sequence it is RECOMMENDED that it close the Sequence. Please see Final and the SequenceClosed fault. Whenever possible the SequenceClosed fault SHOULD be used in place of the SequenceTerminated fault to allow the RM Source to still Receive Acknowledgements.
The following exemplar defines the CloseSequence syntax:
<wsrm:CloseSequence ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
...
</wsrm:CloseSequence>
This element is sent by an RM Source to indicate that the RM Destination MUST NOT accept any new messages for this Sequence. A SequenceClosed fault MUST be generated by the RM Destination when it Receives a message for a Sequence that is already closed.
The RM Source MUST include this element in any CloseSequence messages it sends. The RM Source MUST set the value of this element to the absolute URI (conformant with RFC3986) of the Sequence that is being closed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
A CloseSequenceResponse is sent in the body of a response message by an RM Destination in response to receipt of a CloseSequence request message. It indicates that the RM Destination has closed the Sequence.
The following exemplar defines the CloseSequenceResponse syntax:
<wsrm:CloseSequenceResponse ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
...
</wsrm:CloseSequenceResponse>
This element is sent in the body of a response message by an RM Destination in response to receipt of a CloseSequence request message. It indicates that the RM Destination has closed the Sequence.
The RM Destination MUST include this element in any CloseSequenceResponse message it sends. The RM Destination MUST set the value of this element to the absolute URI (conformant with RFC3986) of the Sequence that is being closed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
When the RM Source has completed its use of the Sequence it sends a TerminateSequence element, in the body of a message, to the RM Destination to indicate that the Sequence is complete and that it will not be sending any further messages related to the Sequence. The RM Destination can safely reclaim any resources associated with the Sequence upon receipt of the TerminateSequence message. Under normal usage the RM Source will complete its use of the Sequence when all of the messages in the Sequence have been acknowledged. However, the RM Source is free to Terminate or Close a Sequence at any time regardless of the acknowledgement state of the messages.
The following exemplar defines the TerminateSequence syntax:
<wsrm:TerminateSequence ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
...
</wsrm:TerminateSequence>
This element is sent by an RM Source to indicate it has completed its use of the Sequence. It indicates that the RM Destination can safely reclaim any resources related to the identified Sequence. The RM Source MUST NOT send this element as a header block. The RM Source MAY retransmit this element. Once this element is sent, other than this element, the RM Source MUST NOT send any additional message to the RM Destination referencing this Sequence.
The RM Source MUST include this element in any TerminateSequence message it sends. The RM Source MUST set the value of this element to the absolute URI (conformant with RFC3986) of the Sequence that is being terminated.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
A TerminateSequenceResponse is sent in the body of a response message by an RM Destination in response to receipt of a TerminateSequence request message. It indicates that the RM Destination has terminated the Sequence.
The following exemplar defines the TerminateSequenceResponse syntax:
<wsrm:TerminateSequenceResponse ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
...
</wsrm:TerminateSequenceResponse>
This element is sent in the body of a response message by an RM Destination in response to receipt of a TerminateSequence request message. It indicates that the RM Destination has terminated the Sequence. The RM Destination MUST NOT send this element as a header block.
The RM Destination MUST include this element in any TerminateSequenceResponse message it sends. The RM Destination MUST set the value of this element to the absolute URI (conformant with RFC3986) of the Sequence that is being terminated.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
On receipt of a TerminateSequence message an RM Destination MUST respond with a corresponding TerminateSequenceResponse message or generate a fault UnknownSequenceFault if the Sequence is not known.
The RM protocol uses a Sequence header block to track and manage the reliable transfer of messages. The RM Source MUST include a Sequence header block in all messages for which reliable transfer is REQUIRED. The RM Source MUST identify Sequences with unique Identifier elements and the RM Source MUST assign each message within a Sequence a MessageNumber element that increments by 1 from an initial value of 1. These values are contained within a Sequence header block accompanying each message being transferred in the context of a Sequence.
The RM Source MUST NOT include more than one Sequence header block in any message.
A following exemplar defines its syntax:
<wsrm:Sequence ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
<wsrm:MessageNumber> wsrm:MessageNumberType </wsrm:MessageNumber>
...
</wsrm:Sequence>
The following describes the content model of the Sequence header block.
This protocol element associates the message in which it is contained with a previously established RM Sequence. It contains the Sequence's unique identifier and the containing message's ordinal position within that Sequence. The RM Destination MUST understand the Sequence header block. The RM Source MUST assign a mustUnderstand attribute with a value 1/true (from the namespace corresponding to the version of SOAP to which the Sequence SOAP header block is bound) to the Sequence header block element.
An RM Source that includes a Sequence header block in a SOAP envelope MUST include this element in that header block. The RM Source MUST set the value of this element to the absolute URI (conformant with RFC3986) that uniquely identifies the Sequence.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The RM Source MUST include this element within any Sequence headers it creates. This element is of type MessageNumberType. It represents the ordinal position of the message within a Sequence. Sequence message numbers start at 1 and monotonically increase by 1 throughout the Sequence. See Section 4.5 for Message Number Rollover fault.
This is an extensibility mechanism to allow different types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The following example illustrates a Sequence header block.
<wsrm:Sequence>
<wsrm:Identifier>http://example.com/abc</wsrm:Identifier>
<wsrm:MessageNumber>10</wsrm:MessageNumber>
</wsrm:Sequence>
The purpose of the AckRequested header block is to signal to the RM Destination that the RM Source is requesting that a SequenceAcknowledgement be sent.
The RM Source MAY request an Acknowledgement Message from the RM Destination at any time by including an AckRequested header block in any message targeted to the RM Destination. An RM Destination that Receives a message that contains an AckRequested header block MUST send a message containing a SequenceAcknowledgement header block to the AcksTo endpoint reference (see Section 3.1) for a known Sequence or else generate an UnknownSequence fault. If a non-mustUnderstand fault occurs when processing an RM header that was piggy-backed on another message, a fault MUST be generated, but the processing of the original message MUST NOT be affected. It is RECOMMENDED that the RM Destination return a AcknowledgementRange or None element instead of a Nack element (see Section 3.6).
The following exemplar defines its syntax:
<wsrm:AckRequested ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
...
</wsrm:AckRequested>
This element requests an Acknowledgement for the identified Sequence.
An RM Source that includes a AckRequested header block in a SOAP envelope MUST include this element in that header block. The RM Source MUST set the value of this element to the absolute URI, (conformant with RFC3986), that uniquely identifies the Sequence to which the request applies.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The RM Destination informs the RM Source of successful message receipt using a SequenceAcknowledgement header block. The RM Destination MAY Transmit the SequenceAcknowledgement header block independently or it MAY include the SequenceAcknowledgement header block on any message targeted to the AcksTo EPR. Acknowledgements can be explicitly requested using the AckRequested directive (see Section 3.5). If a non-mustUnderstand fault occurs when processing an RM header that was piggy-backed on another message, a fault MUST be generated, but the processing of the original message MUST NOT be affected.
A RM Destination MAY include a SequenceAcknowledgement header block on any SOAP envelope targetted to the endpoint referenced by the AcksTo EPR.
During creation of a Sequence the RM Source MAY specify the WS-Addressing anonymous IRI as the address of the AcksTo EPR for that Sequence. When the RM Source specifies the WS-Addressing anonymous IRI as the address of the AcksTo EPR, the RM Destination MUST Transmit any SequenceAcknowledgement headers for the created Sequence in a SOAP envelope to be Transmitted on the protocol binding-specific channel. Such a channel is provided by the context of a Received message containing a SOAP envelope that contains a Sequence header block and/or a AckRequested header block for that same Sequence identifier.
The following exemplar defines its syntax:
<wsrm:SequenceAcknowledgement ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier>
[ [ [ <wsrm:AcknowledgementRange ...
Upper="wsrm:MessageNumberType"
Lower="wsrm:MessageNumberType"/> +
| <wsrm:None/> ]
<wsrm:Final/> ? ]
| <wsrm:Nack> wsrm:MessageNumberType </wsrm:Nack> + ]
...
</wsrm:SequenceAcknowledgement>
The following describes the content model of the SequenceAcknowledgement header block.
This element contains the Sequence Acknowledgement information.
An RM Destination that includes a SequenceAcknowledgement header block in a SOAP envelope MUST include this element in that header block. The RM Destination MUST set the value of this element to the absolute URI (conformant with RFC3986) that uniquely identifies the Sequence. The RM Destination MUST NOT include multiple SequenceAcknowledgement header blocks that share the same value for Identifier within the same SOAP envelope.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The RM Destination MAY include one or more instances of this element within a SequenceAcknowledgement header block. It contains a range of Sequence MessageNumbers successfully accepted by the RM Destination. The ranges SHOULD NOT overlap. The RM Destination MUST NOT include this element if a sibling Nack or None element is also present as a child of SequenceAcknowledgement.
The RM Destination MUST set the value of this attribute equal to the message number of the highest contiguous message in a Sequence range accepted by the RM Destination.
The RM Destination MUST set the value of this attribute equal to the message number of the lowest contiguous message in a Sequence range accepted by the RM Destination.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The RM Destination MUST include this element within a SequenceAcknowledgement header block if the RM Destination has not accepted any messages for the specified Sequence. The RM Destination MUST NOT include this element if a sibling AcknowledgementRange or Nack element is also present as a child of the SequenceAcknowledgement.
The RM Destination MAY include this element within a SequenceAcknowledgement header block. This element indicates that the RM Destination is not receiving new messages for the specified Sequence. The RM Source can be assured that the ranges of messages acknowledged by this SequenceAcknowledgement header block will not change in the future. The RM Destination MUST include this element when the Sequence is closed. The RM Destination MUST NOT include this element when sending a Nack; it can only be used when sending AcknowledgementRange elements or a None.
The RM Destination MAY include this element within a SequenceAcknowledgement header block. If used, the RM Destination MUST set the value of this element to a MessageNumberType representing the MessageNumber of an unreceived message in a Sequence. The RM Destination MUST NOT include a Nack element if a sibling AcknowledgementRange or None element is also present as a child of SequenceAcknowledgement. Upon the receipt of a Nack, an RM Source SHOULD retransmit the message identified by the Nack. The RM Destination MUST NOT issue a SequenceAcknowledgement containing a Nack for a message that it has previously acknowledged within a AcknowledgementRange. The RM Source SHOULD ignore a SequenceAcknowledgement containing a Nack for a message that has previously been acknowledged within a AcknowledgementRange.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The following examples illustrate SequenceAcknowledgement elements:
Message numbers 1...10 inclusive in a Sequence have been accepted by the RM Destination.
<wsrm:SequenceAcknowledgement>
<wsrm:Identifier>http://example.com/abc</wsrm:Identifier>
<wsrm:AcknowledgementRange Upper="10" Lower="1"/>
</wsrm:SequenceAcknowledgement>
Message numbers 1..2, 4..6, and 8..10 inclusive in a Sequence have been accepted by the RM Destination, messages 3 and 7 have not been accepted.
<wsrm:SequenceAcknowledgement>
<wsrm:Identifier>http://example.com/abc</wsrm:Identifier>
<wsrm:AcknowledgementRange Upper="2" Lower="1"/>
<wsrm:AcknowledgementRange Upper="6" Lower="4"/>
<wsrm:AcknowledgementRange Upper="10" Lower="8"/>
</wsrm:SequenceAcknowledgement>
Message number 3 in a Sequence has not been accepted by the RM Destination.
<wsrm:SequenceAcknowledgement>
<wsrm:Identifier>http://example.com/abc</wsrm:Identifier>
<wsrm:Nack>3</wsrm:Nack>
</wsrm:SequenceAcknowledgement>
When an Endpoint is not directly addressable (e.g. behind a firewall or not able to allow incoming connections), an anonymous URI in the EPR address property can indicate such an Endpoint. The WS-Addressing anonymous URI is one such anonymous URI. This specification defines a URI template (the WS-RM anonymous URI) which may be used to uniquely identify anonymous Endpoints.
http://docs.oasis-open.org/ws-rx/wsrm/200608/anonymous?id={uuid}
This URI template in an EPR indicates a protocol-specific back-channel will be established through a mechanism such as MakeConnection, defined below. When using this URI template, “{uuid}” MUST be replaced by a UUID value as defined by RFC 4122[UUID]. This UUID value uniquely distinguishes the Endpoint. A sending Endpoint SHOULD Transmit messages at Endpoints identified with the URI template using a protocol-specific back-channel, including but not limited to those established with a MakeConnection message. Note, this URI is semantically similar to the WS-Addressing anonymous URI if a protocol-specific back-channel is available.
The MakeConnection is a one-way operation that establishes a contextualized back-channel for the transmission of messages according to matching criteria (defined below). In the non-faulting case, if no matching message is available then no SOAP envelopes will be returned on the back-channel. A common usage will be a client RM Destination sending MakeConnection to a server RM Source for the purpose of receiving asynchronous response messages.
The following exemplar defines the MakeConnection syntax:
<wsrm:MakeConnection ...>
<wsrm:Identifier ...> xs:anyURI </wsrm:Identifier> ?
<wsrm:Address ...> xs:anyURI </wsrm:Address> ?
...
</wsrm:MakeConnection>
This element allows the sender to create a transport-specific back-channel that can be used to return a message that matches the selection criteria. Endpoints MUST NOT send this element as a header block.
This element specifies the WS-RM Sequence Identifier that establishes the context for the transport-specific back-channel. The Sequence Identifier should be compared with the Sequence Identifiers associated with the messages held by the sending Endpoint, and if there is a matching message it will be returned. If this element is omitted from the message then the Address MUST be included in the message.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This element specifies the URI (wsa:Address) of the initiating Endpoint. Endpoints MUST NOT return messages on the transport-specific back-channel unless they have been addressed to this URI. This Address property and a message’s WS-Addressing destination property are considered identical when they are exactly the same character-for-character. Note that URIs which are not identical in this sense may in fact be functionally equivalent. Examples include URI references which differ only in case, or which are in external entities which have different effective base URIs. If this element is omitted from the message then the Identifier MUST be included in the message.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed. This allows fine-tuning of the messages to be returned, additional selection criteria included here are logically ANDed with the Address and/or Identifier. If an extension is not supported by the Endpoint then it should return a UnsupportedSelection fault.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
If both Identifier and Address are present, then the Endpoint processing the MakeConnection message MUST insure that any SOAP Envelope flowing on the backchannel MUST be associated with the given Sequence and MUST be addressed to the given URI.
The management of messages that are awaiting the establishment of a back-channel to their receiving Endpoint is an implementation detail that is outside the scope of this specification. Note, however, that these messages form a class of asynchronous messages that is not dissimilar from “ordinary” asynchronous messages that are waiting for the establishment of a connection to their destination Endpoints.
This specification places no constraint on the types of messages that can be returned on the transport-specific back-channel. As in an asynchronous environment, it is up to the recipient of the MakeConnection message to decide which messages are appropriate for transmission to any particular Endpoint. However, the Endpoint processing the MakeConnection message MUST insure that the messages match the selection criteria as specified by the child elements of the MakeConnection element.
When MakeConnection is used, and a message is returned on the transport-specific back-channel, the MessagePending header SHOULD be included on the returned message as an indicator whether there are additional messages waiting to be retrieved using the same selection criteria that was specified in the MakeConnection element.
The following exemplar defines the MessagePending syntax:
<wsrm:MessagePending pending="xs:boolean" ...>
...
</wsrm:MessagePending>
This element indicates whether additional messages are waiting to be retrieved.
This attribute, when set to "true", indicates that there is at least one message waiting to be retrieved. When this attribute is set to "false" it indicates there are currently no messages waiting to be retrieved.
This is an extensibility mechanism to allow different (extensible) types of information, based on a schema, to be passed.
This is an extensibility mechanism to allow additional attributes, based on schemas, to be added to the element.
The absence of the MessagePending header has no implication as to whether there are additional messages waiting to be retrieved.
Faults for the CreateSequence message exchange are treated as defined in WS-Addressing. Create Sequence Refused is a possible fault reply for this operation. Unknown Sequence is a fault generated by Endpoints when messages carrying RM header blocks targeted at unrecognized or terminated Sequences are detected. WSRM Required is a fault generated an RM Destination that requires the use of WS-RM on a Received message that did not use the protocol. All other faults in this section relate to known Sequences. RM Destinations that generate Sequence faults SHOULD send those faults to the same [destination] as Acknowledgement Messages.
Entities that generate WS-ReliableMessaging faults MUST include as the [action] property the default fault action IRI defined below.