[ws-dd] Update to WS-DD FAQ

[Geoff Bullen <Geoff.Bullen@microsoft.com>]

Hi all,

As you know, there is a public facing FAQ about WS-DD on the OASIS web site (http://www.oasis-open.org/committees/ws-dd/faq.php).  There has been some feedback that we should add a response about UDDI and Discovery.  I have worked with Prasad from Software AG and others to create the following additional entry for our FAQ.  If you have any suggestions or feedback, please let me know.  If I don’t hear anything back by the end of this week, I will go ahead and update the FAQ.

Thanks,

Geoff

 

 

What is the difference between WS-Discovery and UDDI?

 

These are two different protocols and the choice of one vs. other or both depends upon the intended use. In general both protocols have the ability to expose a registry of services available on the network, and can in fact be used simultaneously to expose multiple views of the same registry.

UDDI provides a central registry to store information about available Web services. UDDI specifies a protocol for querying and updating this common registry of Web service information. The registry includes information about service providers, the services they host, and the protocols those services implement. The registry also provides mechanisms to add other metadata to any registered information.

With UDDI, the only services that can be discovered are those that have registered with the registry.  Non-registered services may exist on the network, but, if they aren’t registered, clients can’t find or consume them.  Unless a service knows where the registry is, it can’t register itself.  This foreknowledge is usually gained by pre-configuration.

UDDI is intended for heavily managed networks, where the discovery infrastructure (UDDI) and the services are both manually configured and controlled,  and is not intended for unmanaged or ad-hoc network environments.  WS-Discovery is designed to scale up from unmanaged, ad-hoc, and consumer networks to secure enterprise networks.  The following are some of the points to consider when making a decision about the protocol for discovering web services.

·        WS-Discovery provides an ad-hoc mode of operation where you can discover the services without the need of a centralized server to host information about all available services. It provides a protocol to discover dynamically services that are coming and going from a network.  As a service joins the network, it informs its peers of its arrival by broadcasting a Hello message; likewise, when services drop off the network they multicast a Bye message.

·        WS-Discovery is fully compose-able with other WS-* protocol such as WS-Security.  

·        WS-Discovery is lightweight yet can be used in the carefully controlled managed environment.

·        WS-Discovery managed mode doesn’t require the services themselves to be manually controlled, instead it works even when the discovery infrastructure (proxies) are the only parts that are managed.

·        Because UDDI is as up-to-date as it is kept updated, the registry can contain stale, out-dated information about services and entries for services that are no longer available.

UDDI provides additional information about services such as SLA, pricing etc. that helps in deciding a particular service to use at design/development time. WS-Discovery is more focused on dynamically locating the EPR and other metadata about web services at runtime.