• Web services are small units of code
• Web services are designed to handle a limited
set of tasks
• Web Services can convert your applications
• Web Services are published, found, and used
through the Web.
• Web services use XML based communicating
• Web services are independent of operating
• Web services are independent of programming
• Web services connect people, systems and
What are Web Services?
• Web services are application components
• Web services communicate using open
• Web services are self-contained and selfdescribing
• Web services can be discovered using UDDI
• Web services can be used by other
• XML is the basis for Web services
• The basic Web services platform is XML + HTTP.
• XML provides a language which can be used between
different platforms and programming languages and
still express complex messages and functions.
• The HTTP protocol is the most used Internet protocol.
• Web services use the standard web protocols HTTP,
XML, SOAP, WSDL, and UDDI.
• Each XML Web service needs a unique
namespace in order for client applications to
distinguish it from other services on the Web.
• Your XML Web service should be identified by a
namespace that you control. For example, you
can use your company's Internet domain name
as part of the namespace. Although many XML
Web service namespaces look like URLs, they
need not point to actual resources on the Web.
(XML Web service namespaces are URIs.)
• For XML Web services creating using ASP.NET,
the default namespace can be changed using
the WebService attribute's Namespace
• The WebService attribute is an attribute
applied to the class that contains the XML
Web service methods.
• Below is a code example that sets the
public class MyWebService
Benefits of Web Services
• Easier to communicate between applications
• Easier to reuse existing services
• Easier to distribute information to more
• Rapid development
Web services architecture
• The Web services architecture is based upon the
interactions between three primary roles:
service provider, service registry, and service
requestor. These roles interact using publish,
find, and bind operations.
• The service provider is the business that
provides access to the Web service and
publishes the service description in a service
registry. The service requestor finds the service
description in a service registry and uses the
information in the description to bind to a
• A logical view of the Web services architecture
is shown in below.
• In this view of the Web services architecture,
the service registry provides a centralized
location for storing service descriptions.
• A UDDI registry is an example of this type of
• Although it is important, the centralized service
registry is not the only model for Web service
• The simplest form of service discovery is to
request a copy of the service description from
the service provider. After receiving the request,
the service provider can simply e-mail the service
description as an attachment or provide it to the
service requestor on a transferable media, such as
• it requires prior knowledge of the Web service, as
well as the contact information for the service
• there is a need for a distributed service
discovery method that provides references to
service descriptions at the service provider's
• The Web Services Inspection Language
provides this type of distributed discovery
method, by specifying how to inspect a Web
site for available Web services. The WSInspection specification defines the locations
on a Web site where you could look for Web
• WSDL completely describes Web services, the methods
available, and the various ways of calling these
• Web Service Description Language (WSDL)is a W3C
specification which defines XML grammar for describing
• XML Grammar describes details such as:• Where we can find the Web Service (its URI)?
• What are the methods and properties that service
• Data type support. Supported protocols In short its a
bible of what the webservice can do. Clients can
consume this WSDL and build proxy objects that clients
use to communicate with the Web Services.
• UDDI Full form of UDDI is Universal Description,
Discovery and Integration. It is a directory that can
be used to publish and discover public Web Services.
• It hopes to provide a central database where
developers can look to find XML Web services
located all over the globe.
• UDDI is an XML Web service that your applications
can query and receive information from on other
• Web servers that host XML Web services support a
process called discovery, which enables these Web
servers to automatically detect installed Web
Services and provide visitors with a list of available
• Visual Studio gathers information through a process
• DISCO is the abbreviated form of Discovery. It is
basically used to club or group common services
together on a server and provides links to the
schema documents of the services it describes may