This specification intends to meet the following requirements:

This specification defines a method for transmitting notifications to the event sink through the use of the wse:NotifyTo element. Other methods or combination of methods MAY be defined through the use of delivery extensions.

When the wse:NotifyTo element is used within the Delivery element it specifies the endpoint to which notifications are sent. For delivery to addressable endpoints this is sufficient. However, for non-addressable endpoints some additional mechanisms are needed. A subscription manager MAY choose to support mechanisms, such as the specification, to enable delivery of notifications and the SubscriptionEnd message to non-addressable endpoints. See the specification for more information, and an example, of how this would work.

This specification does not mandate how events are serialized into notification messages. Rather, within the Subscribe request message a subscriber can specify a "Format" that indicates the set of rules that MUST be followed when constructing notification messages.

This specification specifies two delivery formats: wrapped and unwrapped. Use of wrapped format indicates that notification messages MUST be contained in a wrapper element defined by this specification. Use of unwrapped format indicates that notification messages are not contained in a wrapper element. Conformant Event Source implementations MUST support both wrapped and unwrapped notifications.

Filtering occurs prior to any formatting of notification messages. This ensures that regardless of what type of formatting might occur, the same Filter dialect/expression can be used to subset the event stream.

In some scenarios the event source itself manages the subscriptions it has created. In other scenarios, for example a geographically distributed publish-and-subscribe system, it might be useful to delegate the management of a subscription to another Web service. To support this flexibility, the response to a subscription request to an event source will include the EPR of a service that the subscriber can interact with to manage this subscription. This EPR MUST be the target for future requests to renew or cancel the subscription. It can address the same Web service (Address and ReferenceParameters) as the event source itself, or it can address some other Web service to which the event source has delegated management of this subscription.

The term "subscription manager" is used in this specification to refer to the Web service that manages the subscription, whether it is the event source itself or some separate Web service.

lists a hypothetical request to create a subscription for storm warnings.

Lines (07-09) in indicate the message is a request to create a subscription, and line (16) indicates that it is sent to a hypothetical event source of ocean events.

While lines (13-15) indicate where a reply is sent, lines (20-29) indicate where and how notifications are to be delivered; there is no requirement that these match. The absence of any extensions to the wse:Delivery or wse:NotifyTo elements indicates that notifications are sent as SOAP messages to the endpoint described in lines (21-28). Note that lines (25-27) illustrate a typical pattern where the event sink lists a reference parameter (line 26) that identifies the subscription and will be included in each notification.

lists a hypothetical response to the request in .

Lines (07-09) in indicate this message is a response to a request to create a subscription, and lines (10-12) indicate that it is a response to the request in . Lines (17-26) provide the subscription manager EPR for this subscription, and line (27) indicates the subscription will not expire.

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 .

This specification uses the following syntax to define normative outlines for messages:

In addition to Message Information Header properties , this specification uses the following properties to define messages:

These properties bind to a SOAP Envelope as follows:

This specification can be used in terms of XML Information Set (Infoset) , even though the specification uses XML 1.0 terminology. Valid Infoset for this specification is the one serializable in XML 1.0, hence the use of XML 1.0.

The term "generate" is used in relation to the various faults defined by this specification to imply that a fault is produced and no further processing SHOULD be performed. In these cases the fault SHOULD be transmitted. However, there might be reasons when a compliant implementation can choose not to transmit the fault - for example, security concerns - in these situations the service MAY choose not to transmit the fault.

The elements defined in this specification MAY be extended at the points indicated by their outlines and schema. 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 that extension. Senders MAY indicate the presence of an extension that has to be understood through the use of a corresponding SOAP Header with a soap:mustUnderstand attribute with the value "1".

In cases where it is either desirable or necessary for the receiver of a request that has been extended to indicate that it has recognized and accepted the semantics associated with that extension, it is RECOMMENDED that the receiver add a corresponding extension to the response message. The definition of an extension SHOULD clearly specify how the extension that appears in the response correlates with that in the corresponding request.

Extension elements and attributes MUST NOT use the Web Services Eventing namespace URI.

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 ) within SOAP Envelopes unless it is compliant with this specification.

Normative text within this specification takes precedence over the XML Schema and WSDL descriptions, which in turn take precedence over outlines, which in turn take precedence over examples.

All messages defined by this specification MUST conform to the WS-Addressing specifications and be sent to a Web service that is addressable by an EPR (see ).

Unless otherwise noted, all IRIs are absolute IRIs and IRI comparison MUST be performed according to section 5.3.1.

For any message defined by this specification, any OPTIONAL elements or attributes in the message MAY be used by senders of the message; however receivers of those messages MUST support those OPTIONAL elements and attributes, unless other behavior is explicitly defined by this specification.

Implementations are expected to support both UTF-8 and UTF-16 as described in XML 1.0.

Implementations of this specification MUST conform to the corrected version of WSDL as defined by the 'WSDL Correction' sections of WS-I Basic Profile 1.2 and WS-I Basic Profile 2.0 .

The XML namespace URI that MUST be used by implementations of this specification is:

lists XML namespaces that are used in this specification. The choice of any namespace prefix is arbitrary and not semantically significant.

The working group intends to update the value of the Web Services Eventing namespace URI each time a new version of this document is published until such time that the document reaches Candidate Recommendation status. Once it has reached Candidate Recommendation status, the working group intends to maintain the value of the Web Services Eventing namespace URI that was assigned in the Candidate Recommendation unless significant changes are made that impact the implementation or break post-CR implementations of the specification. Also see http://www.w3.org/2001/tag/doc/namespaceState.html and http://www.w3.org/2005/07/13-nsuri .

To create a subscription, a subscriber sends a Subscribe request message to an event source. This operation MUST be supported by compliant event sources. The message MUST be of the following form:

The following describes additional, normative constraints on the outline listed above:

Other components of the outline above are not further constrained by this specification.

If included within the Subscribe request message, the wse:NotifyTo and wse:EndTo SHOULD have some cursory validity checking performed before the Subscribe response is returned. While not all errors can be detected prior to sending a message to those EPRs, some obvious ones can be detected. For example, an unsupported transport specified within the wsa:Address IRI. Detecting these errors during Subscribe processing will lessen the chances of the subscriber creating an unusable subscription. If this check is performed and a problem is detected then the event source MUST generate a wse:UnusableEPR fault rather than returning the SubscribeResponse message.

If the event source chooses not to accept a subscription due to the content of the Subscribe message, then the event source MUST generate a SOAP 1.1 Client fault or a SOAP 1.2 Sender fault. If the event source does not accept this subscription due to an internal processing reason and not due to the specific content of the Subscribe message, then the event source MUST generate a SOAP 1.1 Server fault or a SOAP 1.2 Receiver fault which MAY contain the RetryAfter fault detail element.

If the event source accepts a request to create a subscription, it MUST reply with a response of the following form:

The following describes additional, normative constraints on the outline listed above:

Other components of the outline above are not further constrained by this specification.

lists another hypothetical request to create a subscription.

Like the request in , lines (07-09) of indicate the message is a request to create a subscription. Line (19) indicates that it is sent to a hypothetical event source of ocean events.

Lines (13-18) indicate where to send the response to this request, lines (23-30) indicate where to send a SubscriptionEnd message if necessary, and lines (31-34) indicate how and where to send notifications.

Line (41) indicates the event sink would prefer to have the subscription expire on 26 June 2004 at 9:07 PM Pacific time.

Lines (42-44) indicate the event sink only wants weather reports where the speed of wind is greater than 50.

lists a hypothetical response to the request in .

Like the response in , lines (08-10) of indicate this message is a response to a request to create a subscription, and lines (11-13) indicate that it is a response to the request in . Lines (14-17) indicate the response is sent to the event sink indicated in lines (13-18) of . Lines (21-30) provide the address of the subscription manager for this subscription; note that this particular response uses the x:SubID element as a reference parameter to distinguish this subscription EPR from other subscription EPRs. Finally, line (31) indicates the subscription will expire on 26 June 2004 at 9:07 PM Pacific time unless renewed.

To update, or renew, the expiration for a subscription, a subscriber sends a Renew request message to the subscription manager. This operation MUST be supported by compliant subscription managers. The Renew request message MUST be of the following form:

Components of the outline listed above are additionally constrained as for a request to create a subscription (see ). Other components of the outline above are not further constrained by this specification.

If the subscription manager chooses not to renew this subscription, the request MUST fail, and the subscription manager MUST generate a SOAP 1.1 Server fault or a SOAP 1.2 Receiver fault indicating that the renewal was not accepted. This fault MAY contain the RetryAfter fault detail element.

If the subscription manager accepts a request to renew a subscription, it MUST reply with a response of the following form:

Components of the outline listed above are constrained as for a response to a subscribe request (see ). Other components of the outline above are not further constrained by this specification.

lists a hypothetical request to renew the subscription created in .

Lines (07-09) indicate this is a request to renew a subscription. Lines (19-21) contain the reference parameter that indicates the subscription to be renewed is the one created in . Line (25) in indicates the request is to extend the subscription until 26 June 2004 at 9:07 PM Pacific.

lists a hypothetical response to the request in .

Line (17) in indicates the subscription has been extended only until 26 June 2004 at noon.

To get the status of a subscription, the subscriber sends a GetStatus request message to the subscription manager. This operation MUST be supported by compliant subscription managers. The GetStatus request MUST be of the following form:

Components of the outline listed above are not further constrained by this specification.

If the subscription is active, the subscription manager MUST reply with a response of the following form:

Components of the outline listed above are constrained as for a response to a renew request (see ). Other components of the outline above are not further constrained by this specification.

This operation is safe; it will not result in any side effect imputable to the requester. This means that in case of an underlying protocol error that might get unnoticed, resending the same request can be done automatically.

lists a hypothetical request to get the status of the subscription created in .

Lines (07-09) indicate this is a request to get the status of a subscription. Lines (16-21) indicate that the request is sent to the subscription manager for the subscription created in .

lists a hypothetical response to the request in .

Line (17) in indicates the subscription will expire on 26 June 2004 at noon.

Though subscriptions with a non-infinite expiration time will eventually be canceled, to minimize resources, the subscriber SHOULD explicitly cancel a subscription when it no longer wants notifications associated with the subscription.

To explicitly cancel a subscription, a subscriber sends an Unsubscribe request message to the subscription manager. This operation MUST be supported by compliant subscription managers. The Unsubscribe request message MUST be of the following form:

Components of the outline above are additionally constrained only as for a request to renew a subscription (see ). For example, the faults listed there are also defined for a request to cancel a subscription.

If the subscription manager accepts a request to cancel a subscription, it MUST reply with a response of the following form:

Components of the outline listed above are not further constrained by this specification.

lists a hypothetical request to cancel the subscription created in .

Lines (07-09) in indicate the message is a request to cancel a subscription. Lines (16-21) indicate that the request is addressed to the manager for the subscription created in .

lists a hypothetical response to the request in .

If the event source terminates a subscription unexpectedly, and it supports the use of the EndTo EPR, and the EndTo EPR was present in the Subscribe message for that subscription (see ), the SubscriptionEnd message MUST be sent to the endpoint reference indicated by that EPR, if possible.

Note, a subscription expiring as expected is not considered to be an unexpected termination, therefore a SubscriptionEnd message MUST NOT be sent in this case.

The message MUST be of the following form:

The following describes additional, normative constraints on the outline listed above:

Other components of the outline above are not further constrained by this specification.

lists a hypothetical SubscriptionEnd message corresponding to an early termination of the subscription created in .

Line (08) is the action IRI for SubscriptionEnd. Lines (10-13) indicate the message is sent to the EndTo of the subscribe request (lines (23-30) in ). Line (17) indicates the event source is shutting down, and lines (18-20) indicate that the event source was going off line.

The following element MAY be used to convey additional information in the detail element of a fault.

This fault MUST be generated when a request specifies an expiration that is not within the min/max range.

This fault MUST be generated when a request specifies an expiration time and the event source is only capable of accepting expiration durations; for instance, if the event source does not have access to absolute time.

This fault MUST be generated when a Subscribe request contains a filter and the event source does not support filtering.

This fault MUST be generated when a Subscribe request specifies a filter dialect that the event source does not support. This fault MAY contain a list of supported filter dialect IRIs in the Detail property.

This fault MUST be generated when a Subscribe request specifies a delivery format that is not supported by the event source. This fault MAY contain a list of supported delivery format IRIs in the Detail property.

This fault MUST be generated when an event source detects a wse:Subscribe request containing a filter that, for whatever reason, will never evaluate to true.

This fault MUST be generated when an event source detects that the wse:NotifyTo or wse:EndTo EPR is unusable.

This fault MUST be generated when a request specifies a subscription that is not known.

This fault MUST be generated by an event source that does not support /wse:Subscribe/wse:EndTo semantics, in response to a subscription request that contains a wse:EndTo element.

This fault MUST be generated by an event source when the Subscribe request message did not specify a delivery mechanism.

This fault MUST be generated when the data source can not process the filter content.

The information contained in Notifications might be sensitive. In such cases it is advisable to authenticate and authorize subscribers as part of the processing of the Subscribe request. Note that an Event Source may authorize the delivery of Notifications on a per-message basis after the subscription has been created. This might be necessary in cases where the sensitivity of the Notification information is not known at Subscribe time or varies over the lifetime of a subscription.

To protect the Notifications sent over a network, Notifications ought to have the proper authenticity, integrity and confidentiality protections applied.

The ability to subscribe on behalf of a third-party Event Sink could be misused by a malicious Subscriber to create a denial-of-service attack. While it does not remove the ability for such misuse, authenticating Subscribers provides a way to deter and trace the origin of such attempts. Additionally, the authorization of Subscribers reduces the pool of potential attackers.

Once created, subscriptions ought to be treated as protected resources. Renew, GetStatus, and Unsubscribe requests ought to be authenticated and authorized (for example, the identity of the requester ought to be checked against the identity of the entity that performed the original Subscribe request). Likewise SubscriptionEnd messages ought to be authenticated and authorized (for example, the identity of the sender ought to be checked against the identity of the entity that sent the original SubscribeResponse message). Note that authentication and authorization policies (i.e. the rules that define which entities are allowed to perform which requests and the mechanisms by which the identities of these entities are discovered and verified) are particular to individual deployments.

Implementations that perform validity checks on the EPRs used in WS-Eventing (wse:NotifyTo, wse:EndTo) are advised that such checks can be misused to obtain information about a target network. For example, suppose an Event Source implementation verifies the address of NotifyTo EPRs by attempting to create a connection to the EPR's address and faulting the Subscribe request if a connection cannot be created. When deployed within a DMZ, such an Event Source could be exploited by a malicious Subscriber to probe for other, non-visible hosts by guessing target addresses and using them in Subscribe requests. Note that, even if the returned fault does not provide connection information, the time the Event Source spends processing the Subscribe request might reveal if there is a host with the target address.

Implementations that perform validity checks on the EPRs used in WS-Eventing are advised to provide a means to disable such checks in environments where these types of attacks are an issue.

Services indicate support for the WS-Eventing's definition of an event source through the use of the Web Services Policy - Framework and Web Services Policy - Attachment specifications.

This specification defines a policy assertion (wse:EventSource). The normative outline of this assertion is:

The following describes additional, normative constraints on the outline listed above:

The following is an example of a wse:EventSource policy assertion:

In the above example line (02) indicates that this event source supports expiration times as specific times. Line (03) indicates that Filtering is supported and that it supports the XPath 1.0 filter dialect. Lines (04) - (08) indicates that this event source supports sending notifications in the Wrapped format and the Notification WSDL defining the messages is included on lines (05) - (07). Line (09) indicates that the EndTo features is supported. And finally, lines (10) - (12) contains the EventDescription data that describes the syntax of the events that this event source might send.

Services indicate support for the WS-Eventing's definition of a subscription manager through the use of the Web Services Policy - Framework and Web Services Policy - Attachment specifications.

This specification defines a policy assertion (wse:SubscriptionManager). The normative outline of this assertion is:

The following describes additional, normative constraints on the outline listed above: