Web Services: Concepts, Protocols and developmentPrepared By:Mehta Ishani

Outline

•What is a web service?•Why web service?•Web Services Model•Web Services Stack•What is UDDI?•What is WSDL?•What is SOAP?

What is a web service?

•Application components accessible over internet

•Once deployed, can be used by other applications

•XML is the basis for Web services

Standard definitions

•IBM ▫“A Web service is an interface that

describes a collection of operations that are network accessible through standardized XML messaging”

 •Microsoft: XML Web Services

▫“.. provide a way to describe their interfaces in enough detail to allow a user to build a client application to talk to them”

History

•Structured programming •Object-oriented programming•Service oriented programming Hewlett-Packard's e-Speak in 1999 was an

enabler for e-services.Microsoft introduced the name "web

services" in June 2000

Why web services?

•Application and data integration(provides interoperability)

•Versatility(Any platform, Any Language)

•Code re-use(provides flexibility)

•Cost savings(Open Standards)

How does it work?

The basic Web services platform is XML + HTTP.

•SOAP (Simple Object Access Protocol) •UDDI (Universal Description, Discovery

and Integration) •WSDL (Web Services Description

Language)

Web services modelRegistry(UDDI)

Service Requestor

Service Provider

Find Publish

Bind

(SOAP)

(SOAP)

(WSDL)

Web services stack

What is UDDI?

•Universal Description, Discovery and Integration

•UDDI is a directory service where businesses can register and search for Web services.

•Sponsored by OASIS•Uses W3C and IETF Internet standards

such as XML, HTTP, and DNS protocols.

What is UDDI?

•UDDI registry•Search for Web service to obtain WSDL

•For ex. Travel agency can use air line reservation interface

•UDDI Community

What is WSDL?

•Web Services Description Language

•XML-based language for describing Web services and how to access them.

•WSDL is maintained by the W3C.

Major elements

•Port type - describes the operations performed

•Port - specifies an address for a binding•Message – describes name and format of

message•Types - defines the data types•Binding - defines the communication

protocols•Service - specifies the address URL

What is SOAP?

•Simple Object Access Protocol

•SOAP is a simple XML-based protocol that allows applications to exchange information over HTTP.

•SOAP will be developed as a W3C standard

Why SOAP?

•RPC does not support HTTP

•compatibility and security problem, firewalls and proxy servers issues

•HTTP is supported by all Internet browsers and servers.

Major elements

•Envelope –encloses the message itself.•Header (optional) – contains information

relevant to the message•Body – includes the message payload.•Fault (optional) – carries information

about a client or server error within a SOAP message.

namespace

•default namespace for the SOAP envelope:

http://www.w3.org/2001/12/soap-envelope

•default namespace for SOAP encoding and data types is:

http://www.w3.org/2001/12/soap-encoding

SOAP HTTP Binding

•HTTP + XML = SOAP

•A SOAP request could be an HTTP POST or an HTTP GET request.

•Contains two headers• Content-Type - defines the MIME type • Content-Length - number of bytes in the

body

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