1. Advanced Web Technologies Lecture #4 By: Faraz Ahmed

2. Contents 0 Personnel Requirements 0 SQA Tasks 0 Improving SQA

3. WebServices “A software system designed to support interoperable machine-to-machine interaction over a network.” [1]

4. WebServices (simple def) A web service is just a web page meant for a computer to request and process

5. Benefits? 0 Interoperability. 0 Reusability. 0 Connecting Existing Software. 0 Maintainability.

6. WSDL 0 Based on XML 0 Language for describing the service to clients. 0 Description {interactions, Inputs/Outputs, Location, Protocols, Data Formats} 0 Contract between Client and server developers. 0 Alternatives: Web Access Description Language

7. WSDL in its simplest form 1 1 http://w3Schools.com

8. WSDL in its simplest form

9. 0 One-way : The operation can receive a message but will not return a response 0 Request-response : The operation can receive a request and will return a response 0 Solicit-response : The operation can send a request and will wait for a response 0 Notification : The operation can send a message but will not wait for a response

10. Styles[2] How to translate a WSDL into SOAP messages. Document RPC

11. UDDI 0 Universal Description, Discovery and Integration (UDDI) for web Services registration. 0 Platform independent. 0 However lack of public UDDIs has harmed the initiative[3]. 0 UDDI Browser [4]

12. SOAP 0 Simple Object access Protocol 0 CORBA used to be difficult to use. 0 Alternatives: XML-RPC, JSON-RPC 0 The recommendations do not require the use of SOAP for webservices.

13. SOAP 0 Complex datatypes are easily shared as compared to the simplicity of others which hinder such sharing[5]. 0 SOAP services are loosely coupled as compared to their predecessors.

14. Sample Web Services 0 Google's Web Service - access the Google search engine Google's Web Service 0 Amazon's Web Service - access Amazon's product information Amazon's Web Service 0 XMethods XMethods 0 http://www.webservicex.net/ws/wscatlist.aspx

15. The interaction

16. REST[6] 0 Representational State Transfer OPAQUE 0 Each URL represents a different state and that state is transferred. OPAQUE 0 Resources are key elements and identified by URIs 0 Anything of interest is a resource. 0 Gives rise to resource oriented architecture.

17. REST features 0 Client Server 0 Stateless 0 Cacheable 0 Layered System 0 Uniform interface

18. But why Stateless?? 0 Visibility : A server doesn’t have to look further 0 Reliability : Easy recovery from failures 0 Scalability : Limited utilization of server resources.

19. Uniform interface 0 identification of resources; 0 manipulation of resources through representations; 0 self-descriptive messages; and, 0 hypermedia as the engine of application state

20. The Power of URI 0 Maintaining a trail of what and how we got to the point

21. GET: fetch information 0 To fetch a web page, the browser does a GET on some URI and retrieves a representation (HTML, plain text, JPEG, or whatever) of the resource identified by that URI 0 GET is fundamental to browsers because mostly they just browse 0 REST requires a few more verbs to allow taking actions

22. Verbs 0 GET 0 POST 0 PUT 0 DELETE

23. REST vs. SOAP 0 REST 0 Lightweight - not a lot of extra xml markup 0 Human Readable Results 0 Easy to build - no toolkits required 0 Lower Learning Curve 0 Uses the same paradigm as HTTP 0 SOAP 0 Easy to consume - sometimes 0 Rigid - type checking, adheres to a contract 0 Development tools

24. Recommended Reading! 0 How I explained REST to my wife!!! [7]

25. Bibliography 1) “REST”, http://oreilly.com/catalog/pwebserperl/chapter/ch11.pdf, visited on 24 th Jan 2011.http://oreilly.com/catalog/pwebserperl/chapter/ch11.pdf

26. References 1) “Web Services Glossary”, http://www.w3.org/TR/ws-gloss/, visited 23 rd Jan 2011.http://www.w3.org/TR/ws-gloss/ 2) “Which Style of WSDL should I use”, http://www.ibm.com/developerworks/webservices/library/ws- whichwsdl/, visited 23 rd Jan 2011. http://www.ibm.com/developerworks/webservices/library/ws- whichwsdl/ 3) “IBM and Microsoft discontinue Public UDDI Registry”, http://www.webservicessummit.com/News/UDDI2006.htm, visited on 23 rd Jan 2011. http://www.webservicessummit.com/News/UDDI2006.htm 4) “SOAP Client”, http://www.soapclient.com/uddisearch.html, visited on 23 rd Jan 2011.http://www.soapclient.com/uddisearch.html 5) “XML-RPC vs. SOAP”, http://weblog.masukomi.org/writings/xml- rpc_vs_soap.htm, visited on 23 rd Jan 2011.http://weblog.masukomi.org/writings/xml- rpc_vs_soap.htm 6) “Representational State Transfer”, http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm #sec_5_1, visited on 24 th Jan 2011. http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm #sec_5_1 7) “How I explained REST to my wife”, http://tomayko.com/writings/rest-to- my-wife, visited on 24 th Jan 2011.http://tomayko.com/writings/rest-to- my-wife