A Model for Web Services Discovery with QoS SHUPING RAN CIS Eyhab Al-Masri, & Razieh Niazi Paper Reading, Critiquing, and Presenting

Need for QoS-based Discovery of WS Web service textual information is very limited Not easy to distinguish Web services from each other Using keyword-based discovery technique is not efficient

No Support for QoS within Registries  Unfortunately, current UDDI and ebXML implementations do not provide ways to incorporate QoS information  Service Providers advertise their own QoS claims or  Clients perform their own QoS measurements

Suggested Solution: Pros  Ran suggests a QoS Certifier authority that can confirm SP’s QoS claims by issuing a Certification ID  Advantages System provides a way to: offers QoS support for Web services, verify QoS claims, enable clients to search for WS using QoS attributes

Suggested Solution: Cons  Disadvantages  Repetitive SP performs QoS measurements Certifier performs QoS measurements  Extends the current UDDI standard to endorse this solution Problematic: Many UDDI implementations are already existing Does not thoroughly take advantage of UDDI data structure

Suggested Solution: Cons continued…  Implementation Clarity  Not Clear How QoS information is stored within qualityInformation tModel –Unknown How data types are managed or declared –Unknown How qualityInformation tModel is connected to the bindingTemplate –No explanation given  No actual implementation of the system Only examples given for illustration purposes Could not verify if it can be applied

Suggested Solution: Cons continued…  SP must supply QoS information Imposes a restriction that every WS has to have QoS information –“In the propose model, a Web service provider needs to supply information about the company … as well as to supply quality of service information….” Section 2.2 »May not be possible »Allow SPs to think of ways on how to improve QoS measurements  Periodic updates Solution does not discuss or give details as to how frequent QoS information is updated

Suggested Solution: Cons continued…  QoS measurements are not instant Solution implies that QoS certification is quick and easy: 1.the Web service provider first needs to communicate its QoS claims to the service QoS certifier 2.The certifier checks the claims and either certifies or down grade the claim 3.The outcome is sent back to the provider with certification identification information QoS measurements take time  Additional UDDI work “UDDI communicates with the certifier to check the existence of the certification…” –Extra work on UDDI Get data QoS......

Suggested Solution: Cons continued… How QoS measurements are conducted? Using existing tools… Transparent and fair?

Suggested Solution: Cons continued… Who is really the QoS Certifier? Third party? Supervised by UDDI? Middleware? ServiceBroker?

Extending UDDI data structure Current UDDI Data Structure BusinessEntity BusinessService bindingTemplate publisherAssertion tModels Ran’s new UDDI Data Structure businessEntity businessService bindingTemplate publisherAssertion qualityInformation tModels

Interesting Issues:  Service Providers have to go through additional steps to get their Web services published Registration at Certification authority May have to pay fees to get QoS certificate  Section 2.1: “The new UDDI registry is a repository of registered Web services with lookup facilities” UDDI version 2 and 3 already have lookup functionality, uncertain what the author really implies by new UDDI tModels already existed by the time paper was written

Possible Improvements  QoS support should be optional  UDDI is not intended to be a search engine, therefore a service broker may solve the problem Service Provider Service Broker UDDI Registry Publish Retrieve Info Verify QoS Info / Issue URL Web Service Consumer Request/ Respons e 5 Invocation

Conclusion  Although Ran’s solution provides a way to enhance the discovery of Web services using QoS, It lacks implementation results, Requires major change to UDDI standard, and Does not provide adequate level of details on QoS measurements and Certification authority.  QoS measurements must be performed in a transparent manner  Clients should be able to customize discovery process using QoS parameters  Periodic QoS updates and service lifecycle are essential to both SPs and clients

Reference  Ran, S., “A Model for Web Services Discovery with QoS”, ACM SIGecom Exchanges 4(1): pp. 1-10, 2003

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