FUNDAMENTAL OF WEB
SERVICES
WEB SERVICES:-
A Web service is a method of
interaction between two devices over the WWW. It is a software tool provided on internet which
helps us to create client-server service.
It is a software system designed
to support interoperability with various machine interaction over a network.
The web service replies in a language called WSDL (Web Service Description
Language).   
Some of its features
are:-
- They are application
     components
- They  communicate with open protocols
- They  are 
     self-describing
- It can be used by various
     applications
- The basis for web services
     are HTTP and XML
Working
of web services
- The client sends a request
     to the server
-  The Request is  encoded in XML format
-  The Function (GET, POST…)is inserted in
     the file
-  The server receives and decodes the file
-  The received function is executed
-  A new XML file is encoded and is sent
     back to the client. 
WSDL
WSDL is an acronym for Web Services Description
Language. It is a language used for describing web services, how to access them
and locate them. It is usually written in XML.
- It is used to describe Web
     services
- It also locates Web services
UDDI
UDDI is an
acronym for Universal Description, Discovery and Integration. It is a directory
service where businesses can register and search for Web services. It
is a platform-independent framework for describing services, discovering
businesses, and integrating business services by using the Internet.
- It is a directory of web
     service interfaces described by WSDL
- It communicates via SOAP
- It is built into the
     Microsoft .NET platform
TYPES OF WEB SERVICES
-        
Application Programming Interfaces  (API)
-        
 Request services
-        
 REST
architecture 
-        
 SOA
architecture 
-        
SOAP architecture
-        
 World
Wide Web Consortium (W3C) 
API
An application programming interface (API) defines how software elements should communicate with each other.
It is used to ease the work of
programming graphical user interface (GUI) components. An API is based on source
code instead of binary interface. It can take many forms, including an
International Standard such as POSIX, vendor documentation such as the
Microsoft Windows API, e.g., Standard template library in java
API or C++. It is different from an Application
Binary Interface (ABI). In an API, it is based on the source code while an ABI is a
binary interface. For e.g., POSIX is an API, while the Linux
Standard Base is an ABI. 
REST ARCHITECTURE
REST is an acronym
for Representational state transfer. It is an architectural format consisting of a coordinated
set of constraints which is applied on components, connectors, and data
elements, within a distributed hyper media system.
The term REST was introduced and
defined in 2000 by Roy Fielding.
It is  applied to describe the desired web
architecture, for  identifying existing
problems, to compare alternative solutions, and it also ensure that protocol
extensions would not violate the core constraints that make the Web successful.
This format is also applied to the development of Web
services.
The properties of the REST are as
follow:
·        
Performance
·        
Component interactions Scalability
·        
Simplicity of interfaces
·        
Visibility of communication 
·        
portability 
·        
deployment
·        
Reliability
SOAP ARCHITECTURE
SOAP is an acronym for Simple Object Access Protocol.
It is a protocol for accessing web services. It is based on XML.
- It is a communication
     protocol
- This protocol is for
     communication between applications
- It is a format for sending
     messages
- It communicates via Internet
- It  is also platform independent and language
     independent
- It is simple and extensible
It
provides a better way of communication between applications running on
different operating system with different technologies and programming
languages over HTTP, because HTTP is supported by all internet browsers and
servers.
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