This document discusses XML web services and their components. It defines XML web services as software services exposed on the web through the SOAP protocol and described with WSDL and registered in UDDI. It describes how SOAP is used for communication, WSDL describes service interfaces, and UDDI allows for service discovery. Examples of web services are provided. The architecture of web services is shown involving clients, services, and standards. Finally, it discusses how XML data can be transformed to HTML for display in web pages using XSLT transformation rules.

1. Applying XML

2. XML and Web Services
• XML web services are basic building blocks in the
era of distributed computing
• Demand for XML web services:
– Open standards focuses on communication and
collaboration between people and applications
– Web services have become an platform for the
application integration
– Applications have been developed with multiple XML
web services from various sources work together
regardless of where these services resides and how
these services are implemented.

3. Contd..
• XML Web services
– Work with standard web protocols like XML, HTTP and TCP/IP
– exposes many functionality to the user through the web
protocol (SOAP).
– provides a means to describe their interfaces, which allows
the user to build a client application to interact with them and
described in document called WSDL
– must be registered so that users can find them and done
through UDDI.
– allows programs written in different language and in different
architecture to communicate with one another in a standard
way.
• XML web service is defined as the software service
exposed on the web through the SOAP protocol and
described with a WSDL file and registered in the UDDI

4. Contd..
• Examples:
– Stock Quotes
– Weather Forecasts
– Sports Scores
– Calendar Service
• These services can be accessed freely whereas some might
require a subscription to the service
• Makes the programmatic access easier and much more reliable.
• Exposing existing applications as a web service allows users
rapidly to develop new applications based on these web
services.
– For e.g., a web service for purchasing application is developed where
in which this application obtains the price info from a variety of
vendors, allowing the user to select a specific vendor, submitting the
order and then track the shipment details until it is received
– This might in turn use another web service to check the customers
credit, manage the customer’s account.

5. SOAP (Simple Object Access Protocol)
• A communication protocol for Web services.
• A specification which defines the XML format for
messages.
• SOAP message contains the callable function,
parameters required to pass the function which is sent
from the client and the server returns the message
with the results
• SOAP tool kits will translate the function calls from
some language to a SOAP message.
– For example Apache tool kit translates the java function
calls in to SOAP messages
• SOAP is been implemented on many different
hardware and software platforms.

6. WSDL (Web Services Description
Language)
• WSDL file describes the message formats and how
these messages are exchanged.
• It is based on the XML schema standard which
makes the web services interfaces accessible from
variety of platforms and programming languages.
• It also defines where the services are available,
what communication protocol is used.

7. UDDI
• UDDI stands for Universal Discovery Description and
Integration.
• It is like the yellow pages for the Web services.
• Yellow pages are used to search for the company that offers
services we need, read the services offered and contact
someone for more info.
• UDDI directory includes several ways to search for the services
that we need to build our applications.
• Web services can be offered without registering it in the UDDI,
but UDDI is required for the customers to find you.
• For e.g., we can search for providers of a service in a specified
geographic location or for business of a specified type.
• The UDDI directory will then supply info, contacts, links, and
technical data to allow us to evaluate which services meet our
requirements.

8. Web service Architecture

9. HTML with XML
• Data in XML can be described by itself.
• The question of how data is loaded to the application and
displayed to the user is left to the application program.
• Normally web application allows user to display the stored
data through web browser.
• XML data can also be transformed to HTML which can
then be viewed in the web page.
• The transformation of XML to HTML can be done in two
different ways
– DOM/SAX parser which helps in loading XML data into html
page and formatting it in to a HTML document.
– XSLT, which helps in describing the transformation rules from
XML to HTML and display it in the web page.

10. XSLT
• XSLT stands for Extensible Style sheet Language
Transformations
• XSLT is an XML-related Language which helps in
manipulating and transforming XML documents.

11. Contd..

12. XSLT Document
• The root element of the XSL document is
<xsl:stylesheet>
• To include the XSLT is XML document:
<?xml-stylesheet type="text/xsl" href=“filename.xsl"?>