RE: [wsn] WSN-Policy allocations reminder

Notification consumers might only be interested in a portion of the notification message. In many cases, this is handled at the consumer's side, by simply discarding the unwanted information. But in some cases (for example if the notification messages are very large and only a small subset is of interest to the consumer), it is advantageous to have the transformation take place on the notification producer's side.

For this purpose, we define a "NotificationTransformPolicy" policy element to advertise the fact that the notification producer provides the ability to transform the message before sending it.

Options

The "NotificationTransformPolicy" element has the following pseudo-schema:

<SupportedDialect>xs:anyURI<SupportedDialect> +

<xs:any/> *

</NotificationTransformPolicy>

The "SupportedDialect" element contains a URI describing a dialect supported by the notification producer for transformation. The following dialect, "http://www.w3.org/TR/1999/REC-xpath-19991116", represent use of XPath 1.0. Other dialects can be supported.

Context

Support for this policy is advertised by the notification producer. This policy is invoked by the subscriber by placing the "notificationTransform" header in the subscription message. This header must be marked mustUnderstand=true of the consumer is not prepared to handle notifications that were not transformed as prescribed by the "notificationTransform" header.

The pseudo-schema of the "NotificationTransform" header is:

The @dialect contains a URI describing the dialect used to interpret the value of the "NotificationTransform" element. That value can be text or any XML element. The "SupportedDialect" children of the "NotificationTransformPolicy" element indicate what dialects are supported by the notification producer.

If the notification message does not use the "Notify" wrapper, the context for the transformation is the body of the notification message. And the transformed message (including the "TransformedNotification" wrapping) is placed in the SOAP body. If the notification message uses the "Notify" wrapper, the context for the transformation is the "wsnt:Message" element. And the transformed message (including the "TransformedNotification" wrapping) is placed in the "wsnt:Message" element.

In all cases, the modified notification payload is wrapped inside a new element, called "TransformedNotification". There is no expectation that the content of the "TransformedNotification" element validate any schema, just that it is well-formed XML.

Example

Let's assume that the following message is an example notification message:

<s:envelope>

<s:body>

<foo>

<bar1>bar1value</bar1>

<bar2>bar2value</bar2>

</foo>

</s:body>

</s:envelope>

If the subscribe message had included the following header and if this header was accepted by the notification producer:

Then the notification message would instead be:

<s:envelope>

<s:body>

<bar2>bar2value</bar2>

</TransformedNotification>

</s:body>

</s:envelope>

The notifification producer can advertise the following policy element to communicate the fact that it supports this feature:

<SupportedDialect>http://www.w3.org/TR/1999/REC-xpath-19991116<SupportedDialect>

</NotificationTransformPolicy>

Regards,

William

wsn message