Web service

An introduction to building a Web Service:

A Web service consists of a network-accessible service with a formal description of how to connect to and use the service.
The language for formal description of a Web service is XML and through a family of XML interfaces (like SOAP, UDDI and WSDL) will be useful business functions perform.
A Web service description defines a contract for how another system can access the service for data, or in order to get something done.

XHTML is the latest version of HTML.
XHTML consists of all the elements in HTML 4.01 combined with the syntax of XML.
XHTML elements must be properly nested
XHTML elements must always be closed
XHTML elements must be in lowercase
XHTML documents must have one root element

XML stands for EXtensible Markup Language
XML is a markup language much like HTML
XML was designed to describe data
XML tags are not predefined. You must define your own tags
XML uses a Document Type Definition (DTD) or an XML Schema to describe the data
XML with a DTD or XML Schema is designed to be self-descriptive
XML is a W3C Recommendation
XML Namespaces provide a method to avoid element name conflicts.

XSL stands for EXtensible Stylesheet Language. XML Style Sheets
XSLT stands for XSL Transformations
XSLT is the most important part of XSL
XSLT transforms an XML document into another XML document
XSLT uses XPath to navigate in XML documents
XSL describes how the XML document should be displayed!

Web services:
Web services communicate using open protocols
Web services are self-contained and self-describing
Web services can be discovered using UDDI
Web services can be used by other applications
XML is the basis for Web services

The way to create and deploy web-service:
1. Using Apache Axis
2. Bea Weblogic
3. NB 5.0 and Java Web-server 7.0
4. Using Oracle JDeveloper and Oracle App Server

Web services platform elements
* SOAP (Simple Object Access Protocol)
* UDDI (Universal Description, Discovery and Integration)
* WSDL (Web Services Description Language)

SOAP allows applications to exchange information over HTTP.
SOAP stands for Simple Object Access Protocol
SOAP is a communication protocol
SOAP is for communication between applications
SOAP is a format for sending messages
SOAP is designed to communicate via Internet
SOAP is platform independent
SOAP is language independent
SOAP is based on XML
SOAP is simple and extensible
SOAP allows you to get around firewalls
SOAP will be developed as a W3C standard

UDDI is a directory service where businesses can register and search for Web services.
* UDDI stands for Universal Description, Discovery and Integration
* UDDI is a directory for storing information about web services
* UDDI is a directory of web service interfaces described by WSDL
* UDDI communicates via SOAP
* UDDI is built into the Microsoft .NET platform

WSDL is an XML-based language for describing Web services and how to access them.
* WSDL stands for Web Services Description Language
* WSDL is written in XML
* WSDL is an XML document
* WSDL is used to describe Web services
* WSDL is also used to locate Web services
* WSDL is not yet a W3C standard

A WSDL document describes a web service.
It specifies the location of the service and the operations (or methods) the service exposes.
(the message format and protocol details for a web service.)

The major elements:
portType: The operations performed by the web service
The port defines the connection point to a web service. It can be compared to a function library (or a module, or a class) in a traditional programming language. Each operation can be compared to a function in a traditional programming language.

message: The messages used by the web service
types: The data types used by the web service
binding: The communication protocols used by the web service


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