XML Document Instance

The following example is called an XMl document instance,Which means that it represents one possible set of data for a particular markup language.It might be saved as a file or sent over the internet as the payload of a SOAP message.
You see two XML document instance below but both are different SInce it has same elements, It is considered as different XML document instance because of the Data represented are different.

<address>
<type>HOME</type>
<Street>5577 High street</street>
<city>Erie</city>
<state>PA</state>
<zip>16507</zip>
</address>

<address>
<type>OFFICE</type>
<Street>5511 main street</street>
<city>Erie</city>
<state>PA</state>
<zip>16507</zip>
</address>

What is XML?

XML is used to organize documents and business data. XML files can be stored or transmitted between two applications on a network. Basically, they are just plain text documents that contain special tags that label different parts of a document or fields of data.

XML is a framework for defining markup languages, there is no fixed collection of markup tags, and User can define their own tags. XML language is targeted at its own application domain, but the languages will share many features.Following is the sample XML codes:

<?xml version="1.0" encoding="UTF-8"?>

<lunch_menu>

<food>

<name>Cripsy Green Salads</name>

<price>$3.95</price>

<description>Cripsy Green Salads with Italian Dressing</description>

<calories>150</calories>

</food>

</lunch_menu>

<?xml version="1.0" encoding="UTF-8"?>
<contact>
<address>
<name>Oracle</name>
<street>111 Main Street</street>
<city>Santa Barbara</city>
<state>CA</state>
</address>

<phonenumber>

<areacode>814</areacode>

<number>345-6789</number>

</phonenumber>

</contact>

XML is the foundation of all the other webservices technologiesThere is only one version for XML XML1.0 which is managed by the World Wide Web Consortium (W3C).

Namespace Prefixes

The above Table shows the namespace prefixes used in the WS-I Basic Profile 1.0

Purpose of Web Services

Web service was too general to fulfill technology's main purpose,interoperability. The main purpose of webservices technologies is to allow applications on different platforms to exchange business data.There are two major factors to use web services,both remarkably straightforward that someone else has information that you require, or you have information you wish to provide to others.

Web service technologies are used for Application to application(A2A) integration or Business to Business communication.A2A refers to disparate applications within single organization communicating and exchanging data-A2A is also known as Enterprise Application Integration(EAI).B2B refers to multiple Organizations,typically business partners,exchanging data.Web service technologies today are mostly used in A2A/EAI settings.But they are also in B2B.
Another major use of web services is it can provide any level of security, from a completely open service open to all who request it,to a private service with transfers happening over SSL and client-side certificates to validate identities.

Also Web services make use of technology that is existing in already deployed Webserver,database and others.

Web services can help manage costs and easy integration with businesses.

Understanding Web Services

Java and Web Services seem to be everywhere, these technologie saw rapid adaption and today they are the essential technology of Enterprise systems. Web Services it is a revolutionary technology. "Web Services is a software system designed to support interoperable machine-to-machine interaction over a network". In term Webservices describes the standardized way of integrating web based applications using XML, SOAP, WSDL and UDDI.

• XML is used to define the data.
• SOAP is used to transfer the data.
• WSDL used to describe the services available.
• UDDI is used to list the available services.

Simply Web services share business logic, data and process through a programmatic interface across a network such as internet and executed on a remote system hosting the requested services.

We'll see more about the Web Services Standards (XML,SOAP,WSDL and UDDI) and J2EE Web Services APIs (JAX-RPC,SAAJ,JAXR and JAXP) in detail later in this blog.

• XML: eXtensible Markup Language.
• SOAP: Simple Object Access Protocol.
• WSDL: Web Services Description Language.
• UDDI: Universal Description,Discovery and Integration.