Designing the Solution


In the Windows Communication Foundation, everything about how software entities communicate is controlled through the specification of addresses, bindings, and contracts. Addresses identify where software entities are located on the network. Bindings specify protocols by which messages may be transmitted between a service and its clients. Contracts describe the messages that the service can understand, and how the service will respond to the messages it receives.

In building a REST service using the Windows Communication Foundation, a unique address will be provided for the service, as well as a binding that specifies the use of the HTTP protocol to communicate with the service, because all REST services use HTTP to exchange messages. Also, because the service will be used to publish an RSS feed, the binding will have to be configured for the exchange of XML messages that are not in the SOAP format. Henceforth, messages that are not in the SOAP format will be referred to as plain old XML, or POX, messages. The contract for the service should be one by which an empty request from an RSS aggregator receives the POX message of the RSS feed in response.

Note that Wikipedia defines the term POX in such a way that one might conceivably not count an RSS feed as being an instance of POX (Wikipedia 2005a). However, there is some evidence that the original use of the term was to refer to XML messages in any format other than the SOAP format (Box 2005).

To allow the RSS aggregator to control what a child can see of the contents of the RSS feed, the RSS 2.0 specification's support for adding new tags, or extensions, to the basic RSS format will be leveraged (Winer 2005). One extension tag that will be added is one for specifying a rating for the content of the field: whether it is for all ages, or only for adults. Of course, parents cannot rely on the authors of RSS feeds to accurately rate their content independently. So the content ratings will be digitally signed, along with links to content, with the private key of the certificate of some organization that parents might trust to rate the content of RSS feeds. The RSS aggregator will use the public key of that organization's certificate to verify the certificate of the digitally signed content rating of the feed, and thereby know that it can trust the rating and the links to content, and behave accordingly to show or not show the content to a child. With these simple extensions to RSS, one could establish a system not entirely unlike the Comics Code Authority that reassured parents of the content of mainstream American comic books for almost half a century from the mid-1950s to 2001 (Wikipedia 2005b).




Presenting Microsoft Communication Foundation. Hands-on.
Microsoft Windows Communication Foundation: Hands-on
ISBN: 0672328771
EAN: 2147483647
Year: 2006
Pages: 132

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