1. Introduction to Web Services
By Karim Zaveri

2. What is a Web Service
Method of communication that allows software systems to exchange data over the Internet
W3C defines a Web service as “a software system designed to support interoperable machine-to-machine interaction over a network”
Based on Web based standard protocols: XML and HTTP
Operating System, Platform, and Language independent

3. History
Need for a standard way for businesses to communicate over a network
Many past attempts for standard communication protocol failed, e.g. EDI, CORBA, DCOM
Complex and difficult to implement, costly and inflexible
HTTP and XML Web standards paved way for standardized M2M communication
XML-RPC was first attempt by Microsoft. Predecessor to SOAP
Simple Object Access protocol (SOAP) designed in 1988 by Dave Winer, Don Box, Bob Atkinson, and Mohsen Al-Ghosein for Microsoft
SOAP was platform agnostic, flexible, and general-purpose

4. History (cont’d)
IBM was first to accept SOAP and work with Microsoft (2000). They worked together to come up with WSDL
Need for global registry to advertise and locate Web services
IBM, Microsoft, and Ariba developed UDDL (Universal Description, Discovery, and Integration)
Oracle, HP, Sun, IBM, and Microsoft accepted SOAP, WSDL, UDDL as a de-facto standard for Web Services (2000)
SOAP 1.2 became a W3C recommendation on June 24, 2003
WSDL 2.0 became a W3C recommendation on June 2007

5. Benefits of using Web Services
Interoperability: seamless communication and exchange of data between various systems. Platform, system, and language independent. Loosely coupled
Usability: accessibility of Web Services from other businesses
Reusability: ease of reusability of previously developed Web Services
Deployability: deployed over standard Internet technologies, messages can easily pass through firewalls

6. Web Service Components
Service Provider – the software system that would process the request and provide the data to the requestor
Service Requestor – the software system that requests data by calling a service
Service Registry –
Also known as UDDI (Universal Description, Discovery and Integration)
a directory or registry identifying software systems and the services they provide

7. UDDI (Universal Description, Discovery, and Integration
Mechanism to register and locate web service applications
Sponsored by the Organization for the Advancement of Structured Information Standards (OASIS)
Originally proposed as a core Web service standard
Uses WSDL to describe interfaces to web services
Helps with the “discovery” of web services by various business service providers
Not as widely adopted as its designers had hoped

8. SOAP (Simple Object Access protocol)
Protocol specification for web service data exchange
Foundation layer for web service protocol stack
Uses XML for message format
Easily extensible, e.g. WS-Security, WS-Routing
Can operate under any transport protocol, e.g. HTTP, UDP. Popular transport protocol is HTTP
Language and platform independent

9. SOAP Elements Envelope: Identifies the XML document as a SOAP message
Header: Contains header information
Body
Message data: Contains call and response information
Fault (optional): Provides information about errors that occurred while processing the message

10. SOAP Example - Request
<?xml version="1.0"?> <soap:Envelope xmlns:soap=" soap:encodingStyle=" <soap:Body xmlns:m="   <m:GetStockPrice>     <m:StockName>IBM</m:StockName>   </m:GetStockPrice> </soap:Body> </soap:Envelope>

11. SOAP Example - Response
<?xml version="1.0"?> <soap:Envelope xmlns:soap=" soap:encodingStyle=" <soap:Body xmlns:m="   <m:GetStockPriceResponse>     <m:Price>34.5</m:Price>   </m:GetStockPriceResponse> </soap:Body> </soap:Envelope>

12. WSDL Web Services Description Language XML based language
Describes Service Providers Web Service Operations
Serves as a contract between service provider and service requester
Describes the services, how to call them, communication protocol to use, and the resultant data

13. WSDL structure
Cristcost, Comparison and analogies between WSDL 1.1 and 2.0 structures. [Image]. Retrieved from

14. Web Services Process
Basic architecture of the Web services framework. [Image]. Retrieved from

15. Classes of Web Services
2 Major classes of web services
Big Web Services
RESTful Web Services

16. Big Web Services Uses XML messages Based on SOAP standard
Often reference WSDL to describe the web services offered
Popular with traditional enterprise systems
Includes architecture to handle complex requirements like security, transactions, addressing, trust, and coordination.
Useful for solutions that require Asynchronous processing and stateful operations

17. RESTful Web Services
REpresentational State Transfer (REST) is an architectural style – neither a standard nor a protocol
Manipulates XML representations of web resources using uniform set of stateless operations
Representation of web resources are identified by URI (Uniform Resource Identifier)
Based on HTTP protocol and its methods (GET, PUT, POST, DELETE)
Does NOT use WSDL – both parties require mutual understanding of the data being exchanged
Useful for solutions that are completely stateless and requiring lightweight infrastructure (less bandwidth usage)

18. JSON-RPC
A simple stateless Remote Procedure Call (RPC) protocol that uses JSON formatted messages. A very simple protocol similar to XML-RPC (predecessor to SOAP)
JSON (JavaScript Object Notation) is a language-independent data format derived from JavaScript scripting language
JSON is a human-readable open-standard format, used as an alternative to XML,
Useful for real-time server-to-browser communication
Supports multiple web service calls that maybe answered out of order
Requests are send through HTTP or a TCP/IP socket
Allows sending of notifications (server does not require sending a response back)

19. Web Service specifications
Variety of specifications of varying degrees supported by various standard bodies and entities
Specifications may complement, overlap, and compete with each other
Extensions to standardized specifications like SOAP, WSDL, UDDI, etc.
WS- is the prefix used to indicate specifications associated with Web Services
Messaging specifications: WS-Notification, WS-Addressing, WS-Transfer
Metadata Exchange specifications: WS-Policy, WS-Discovery
Security Specifications: WS-Security, WS-Trust

20. References From EDI To XML And UDDI: A Brief History Of Web Services
Wikipedia WSDL page
Wikipedia SOAP page
An Introduction to the Web Services Architecture and Its Specifications
Types of Web Services – Big and RESTful
W3C WSDL 1.1

21. THE END