Web services allow applications to communicate over the Internet through open standards and protocols. They are self-contained, modular applications that can be described, published, located, and invoked over a network, typically the Internet. Key technologies that enable web services include XML, SOAP, WSDL, and UDDI. SOAP is a messaging protocol that allows communication between applications over HTTP. WSDL describes how to access web services and what operations they perform. UDDI provides a registry for businesses to publish and discover web services.

1. 1 Mehta Ishani
2nd
M.E.(CSE)
Web Services: Concepts, Protocols and
development
What is a web service?
They are pieces of business logic that can be accessed over the
Internet.
A Web Service is an application component accessible over open
protocols
Web services communicate using standards-based Web technologies
including HTTP and XML-based messaging.
Web services are self-contained and self-describing
Once deployed Web services can be used by other applications
Examples:-e-commerce, Google, Amazon and eBay are providing web
services
Standard definition
• 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
– “.. expose useful functionality to Web users through a standard
Web protocol”
– “.. provide a way to describe their interfaces in enough detail
to allow a user to build a client application to talk to them”
– “.. are registered so that potential users can find them easily”
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

2. 2 Mehta Ishani
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M.E.(CSE)
Why web services
Web services provide several technological and business
benefits, a few of which include:
 Application and data integration
WS provides inherent interoperability with using vendor,
platform, and language independent XML technologies and the
ubiquitous HTTP as a transport mean so that any application
can communicate with any other application using Web
services.
The client only requires the WSDL definition to effectively
exchange data with the service – and neither part needs to
know how the other is implemented or in what format its
underlying data is stored. These benefits allow
organizations to integrate disparate applications and data
formats with relative ease.
 Versatility
Web services are also versatile by design. They can be
accessed by humans via a Web-based client interface, or
they can be accessed by other applications and other Web
services.
A client can even combine data from multiple Web services
to, for instance, present a user with an application to
update sales, shipping, and ERP systems from one unified
interface – even if the systems themselves are
incompatible. Because the systems exchange information via
Web services, a change to the sales database, for example,
will not affect the service itself.
 Code re-use
Code re-use is another positive side-effect of Web
services' interoperability and flexibility. One service
might be utilized by several clients, all of which employ
the operations provided to fulfill different business
objectives. Instead of having to create a custom service
for each unique requirement, portions of a service are
simply re-used as necessary.

3. 3 Mehta Ishani
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M.E.(CSE)
 Cost savings
Easy interoperability means the need to create highly
customized applications for integrating data, which can be
expensive, is removed.
Existing investments in systems development and
infrastructure can be utilized easily and combined to add
additional value.
Since Web services are based on open standards their cost
is low and the associated learning curve is smaller than
that of many proprietary solutions.
Finally, Web services take advantage of ubiquitous
protocols and the Web infrastructure that already exists in
every organization, so they require little if any
additional technology investment.
How does it Work?
The basic Web services platform is XML + HTTP.
The HTTP protocol is the most used Internet protocol.
XML provides a language which can be used between different
platforms and programming languages and still express complex
messages and functions.
Web services platform elements
 SOAP (Simple Object Access Protocol)
 UDDI (Universal Description, Discovery and Integration)
 WSDL (Web Services Description Language)
Web Services Model

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M.E.(CSE)
Web Services Stack
What is UDDI?
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
UDDI is a standard sponsored by OASIS (Organization for the
Advancement of Structured Information Standards)
UDDI uses World Wide Web Consortium (W3C) and Internet
Engineering Task Force (IETF) Internet standards such as XML,
HTTP, and DNS protocols.
UDDI provides businesses a uniform way of listing their services
and discovering services offered by other organizations.

5. 5 Mehta Ishani
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Registering a Web service in a UDDI registry is an optional
step, and UDDI registries can be public or private (i.e.
isolated behind a corporate firewall).
To search for a Web service, a developer can query a UDDI
registry to obtain the WSDL for the service he/she wishes to
utilize.
How can UDDI be Used
If the industry published an UDDI standard for flight rate
checking and reservation, airlines could register their services
into an UDDI directory. Travel agencies could then search the
UDDI directory to find the airline's reservation interface. When
the interface is found, the travel agency can communicate with
the service immediately because it uses a well-defined
reservation interface.
Who is Supporting UDDI?
UDDI is a cross-industry effort driven by all major platform and
software providers like Dell, Fujitsu, HP, Hitachi, IBM, Intel,
Microsoft, Oracle, SAP, and Sun, as well as a large community of
marketplace operators, and e-business leaders.
Over 220 companies are members of the UDDI community.
What is WSDL?
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 also used to locate Web services
WSDL describes a web service, along with the message format and
protocol details for the web service.
WSDL is maintained by the W3C.
Through the WSDL, a Web services client learns where a service
can be accessed, what operations the service performs, the
communication protocols the service supports, and the correct
format for sending messages to the service.

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Six main elements:
Port type – groups and describes the operations performed by the
service through the defined interface.
Port – specifies an address for a binding, i.e., defines a
communication port.
Message – describes the names and format of the messages
supported by the service.
Types – defines the data types (as defined in an XML Schema)
used by the service for sending messages between the client and
server.
Binding – defines the communication protocols supported by the
operations provided by the service.
Service – specifies the address (URL) for accessing the service.
The WSDL document that describes a Web service acts as a
contract between Web service client and server.
By adhering to this contact the service provider and consumer
are able to exchange data in a standard way, regardless of the
underlying platforms and applications on which they are
operating.
What is SOAP?
The basic Web services platform is XML plus HTTP.
SOAP stands for Simple Object Access Protocol
SOAP is platform independent and language independent
SOAP is simple and extensible
SOAP allows you to get around firewalls
SOAP will be developed as a W3C standard
SOAP is a simple XML-based protocol that allows applications
to exchange information over HTTP.
SOAP is a protocol for accessing a web service.

7. 7 Mehta Ishani
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Why SOAP?
It is important for application development to allow Internet
communication between programs.
Today's applications communicate using Remote Procedure Calls
(RPC) between objects like DCOM and CORBA, but HTTP was not
designed for this. RPC represents a compatibility and security
problem; firewalls and proxy servers will normally block this
kind of traffic.
A better way to communicate between applications is over HTTP,
because HTTP is supported by all Internet browsers and servers.
SOAP was created to accomplish this.
SOAP provides a way to communicate between applications running
on different operating systems, with different technologies and
programming languages.
Major elements:
Envelope – specifies that the XML document is a SOAP message;
encloses the message itself.
Header (optional) – contains information relevant to the
message, e.g., the date the message was sent, authentication
data, etc.
Body – includes the message payload.
Fault (optional) – carries information about a client or server
error within a SOAP message.
Data is sent between the client(s) and the Web service using
request and response SOAP messages, the format for which is
specified in the WSDL definition. Because the client and server
adhere to the WSDL contract when creating SOAP messages, the
messages are guaranteed to be compatible.
All the elements above are declared in the default namespace for
the SOAP envelope:
http://www.w3.org/2001/12/soap-envelope
and the default namespace for SOAP encoding and data types is:
http://www.w3.org/2001/12/soap-encoding
Syntax Rules

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Here are some important syntax rules:
 A SOAP message MUST be encoded using XML
 A SOAP message MUST use the SOAP Envelope namespace
 A SOAP message MUST use the SOAP Encoding namespace
 A SOAP message must NOT contain a DTD reference
 A SOAP message must NOT contain XML Processing Instructions
SOAP HTTP Binding
A SOAP method is an HTTP request/response that complies with the
SOAP encoding rules.
HTTP + XML = SOAP
A SOAP request could be an HTTP POST or an HTTP GET request.
The HTTP POST request specifies at least two HTTP headers:
Content-Type and Content-Length.
Content-Type
The Content-Type header for a SOAP request and response defines
the MIME type for the message and the character encoding
(optional) used for the XML body of the request or response.
Content-Length
The Content-Length header for a SOAP request and response
specifies the number of bytes in the body of the request or
response.