Basic Web Service concepts

                                  Web service is a way of communication that allows interoperability between different applications on different platforms, for example, a java based application on Windows can communicate with a .Net based one on Linux. The communication can be done through a set of XML messages over HTTP protocol.
                                 Web services are browsers and operating system independent service, which means it can run on any browser without the need of making any changes. Web Services take Web-applications to the Next Level.The World Wide Web Consortium (W3C) has defined the web services. According to W3C, “Web Services are the message-based design frequently found on the Web and in enterprise software. The Web of Services is based on technologies such as HTTP, XML, SOAP, WSDL, SPARQL, and others.”
Why you need to learn web services:
 
Reuse already developed(old) functionality into new software: Lets understand with very simple example.Lets say you are developing a finance software for a company on java and you have old .net software which manages salary of employees.So rather then developing new software for employee part,you can use old software and for other parts like infrastructure you can develop your own functionalities.
Usability Web Services allow the business logic of many different systems to be exposed over the Web. This gives your applications the freedom to chose the Web Services that they need. Instead of re-inventing the wheel for each client, you need only include additional application-specific business logic on the client-side. This allows you to develop services and/or client-side code using the languages and tools that you want.
Interoperability :This is the most important benefit of Web Services. Web Services typically work outside of private networks, offering developers a non-proprietary route to their solutions.Web Services also let developers use their preferred programming languages. In addition, thanks to the use of standards-based communications methods, Web Services are virtually platform-independent.
Loosely Coupled:Each service exists independently of the other services that make up the application. Individual pieces of the application to be modified without impacting unrelated areas.
Ease of Integration:Data is isolated between applications creating ’silos’. Web Services act as glue between these and enable easier communications within and across organisations.
Deployability :Web Services are deployed over standard Internet technologies. This makes it possible to deploy Web Services even over the fire wall to servers running on the Internet on the other side of the globe. Also thanks to the use of proven community standards, underlying security (such as SSL) is already built-in.

Some jargons used in Web services:
Simple Object Access Protocol(SOAP):
SOAP is a protocol specification for exchanging structured information in the implementation of Web services in computer networks. It relies on XML as its message format.
Web Service Description Language(WSDL):
WSDL stands for Web Service Description Language. It is an XML file that describes
the technical details of how to implement a web service, more specifically the URI,
port, method names, arguments, and data types. Since WSDL is XML, it is both
human-readable and machine-consumable, which aids in the ability to call and bind to
services dynamically.
Elements of WSDL are:
Description:
It is the root element of a WSDL 2.0 file. It usually contains a set of name space declarations which are used throughout the WSDL file. 
Types:
The WSDL types element describes the data types used by your web service.Data types are usually specified by XML schema.It can be described in any language as long as your web services API supports it.

Binding:
The WSDL binding element describes how your web service is bound to a protocol. In other words, how your web service is accessible. To be accessible, the web service must be reachable using some network protocol. This is called "binding" the web service to the protocol.

Interface:
The WSDL interface element describes the operations supported by your web service.It is similar to methods in programming language.Client can only call one opertion per request. 

Service:
It describes the endpoint of your web service. In other words, the address where the web service can be reached.

Endpoint:
The endpoint element describes the address of the web service. The endpoint binding attribute describes what binding element this endpoint uses.i.e. protocol with which you will access web service. The address attribute describes the URI at which you can access the service.

Message:
The message element describes the data being exchanged between the Web service providers and consumers.

Sample WSDL file:
   <?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions targetNamespace="http://webservices.javapostsforlearning.arpit.org" xmlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://webservices.javapostsforlearning.arpit.org" xmlns:intf="http://webservices.javapostsforlearning.arpit.org" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<!--WSDL created by Apache Axis version: 1.4
Built on Apr 22, 2006 (06:55:48 PDT)-->
 <wsdl:types>
  <schema elementFormDefault="qualified" targetNamespace="http://webservices.javapostsforlearning.arpit.org" xmlns="http://www.w3.org/2001/XMLSchema">
   <element name="sayHelloWorld">
    <complexType>
     <sequence>
      <element name="name" type="xsd:string"/>
     </sequence>
    </complexType>
   </element>
   <element name="sayHelloWorldResponse">
    <complexType>
     <sequence>
      <element name="sayHelloWorldReturn" type="xsd:string"/>
     </sequence>
    </complexType>
   </element>
  </schema>
 </wsdl:types>
   <wsdl:message name="sayHelloWorldRequest">
      <wsdl:part element="impl:sayHelloWorld" name="parameters"/>
   </wsdl:message>
   <wsdl:message name="sayHelloWorldResponse">
      <wsdl:part element="impl:sayHelloWorldResponse" name="parameters"/>
   </wsdl:message>
   <wsdl:portType name="HelloWorld">
      <wsdl:operation name="sayHelloWorld">
         <wsdl:input message="impl:sayHelloWorldRequest" name="sayHelloWorldRequest"/>
         <wsdl:output message="impl:sayHelloWorldResponse" name="sayHelloWorldResponse"/>
      </wsdl:operation>
   </wsdl:portType>
   <wsdl:binding name="HelloWorldSoapBinding" type="impl:HelloWorld">
      <wsdlsoap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
      <wsdl:operation name="sayHelloWorld">
         <wsdlsoap:operation soapAction=""/>
         <wsdl:input name="sayHelloWorldRequest">
            <wsdlsoap:body use="literal"/>
         </wsdl:input>
         <wsdl:output name="sayHelloWorldResponse">
            <wsdlsoap:body use="literal"/>
         </wsdl:output>
      </wsdl:operation>
   </wsdl:binding>
   <wsdl:service name="HelloWorldService">
      <wsdl:port binding="impl:HelloWorldSoapBinding" name="HelloWorld">
         <wsdlsoap:address location="http://localhost:8080/SimpleSOAPExample/services/HelloWorld"/>
      </wsdl:port>
   </wsdl:service>
</wsdl:definitions>
Universal Description, Discovery and Integration(UDDI):
UDDI stands for Universal Description, Discovery and Integration.It is a directory service. Web services can register with a UDDI and make themselves available through it for discovery

Web service design approaches:

Contract last or Bottom up approach:
When using contract last approach,you first write your java code then you create web service contract(WSDL) .There are various kinds of tools which can generate WSDL on the basis of java code.
s
It  is reverse of contract first.Here you first define web service contract.You define all the elements of WSDL first then after that you create your java logic.

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New High-Tech Plants Could Detect Bombs or Chemical Weapons

Interesting news to share with you friends , Researchers have embedded a tiny structures called carbon nanotubes , which is fixed the energy-making factories of plants, increasing their light-capturing ability by 30 percent. Using other carbon nanotubes, the researchers made plants sensitive to the atmospheric pollutant nitric acid.Plants repair themselves, they were environmentally stable outside, they survive in harsh environments, and they provide their own power source and water distribution.
The researchers were originally working on building self-repairing solar cells based on plant cells, which convert light into chemical energy, in the form of sugars and other compounds, by a process known as photosynthesis. The process relies on chloroplasts, the tiny energy factories inside plant cells.
To protect chloroplasts against the damage, the researchers embedded the chloroplasts with tiny antioxidant particles, or nanoparticles, which scoop up oxygen radicals and other highly reactive molecules. In order to deliver the nanoparticles, the researchers coated them in a highly charged molecule that allowed the particles to penetrate the fatty membranes of the chloroplasts. As a result of the nanoparticles, the amount of damaging molecules plummeted.Next, the researchers coated tiny cylinders called carbon nanotubes in negatively charged DNA and embedded them in the chloroplasts. The nanotubes worked like artificial antennae that allowed the plant to capture more light than usual.The rate of photosynthesis in the chloroplasts with embedded nanotubes was almost 50 percent greater than in isolated chloroplasts that lacked the nanotubes. When the researchers embedded both antioxidant nanoparticles and carbon nanotubes in the chloroplasts, these cells continued to function outside of the plant for even longer.
The researchers also improved the energy efficiency of living plants. They infused nanoparticles into a small flowering plant called Arabidopsis thaliana, improving photosynthesis by 30 percent.
Researchers also found a way to turn the Arabidopsis thaliana plants into chemical sensors, using carbon nanotubes that detect the pollutant nitric oxide, which is produced by combustion.The researchers have previously developed carbon nanotubes that detect the explosive TNT and the nerve gas sarin, so they might be able to turn plants into sensors to detect these toxins at low concentrations. Nanobionic plants could also be used to monitor pesticides, fungal infections or bacterial toxins.
nFinally this invention lead to powerful evolution in the field of Biotechnology. A pollution free bright future is on the way with help of these Engineering plants.

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Sony and Panasonic unveil 300 GB Archival Discs for long-term storage

Sony and Panasonic have jointly announced a new type of optical disc, which they're dubbing the Archival Disc. As the name of the media would suggest, it's aimed at long-term data storage, both through large capacities and durability.

When Archival Discs become commercially available in 2015, they'll sport 300 GB of storage through triple-layer, double-sided discs. Interestingly, the laser wavelength to read Archival Discs is identical to Blu-rays at 405 nm, although the track pitch has decreased from 320 nm to 225 nm. Sony and Panasonic have implemented cross talk cancellation technology, making the discs just as readable despite the narrower tracks.

Each disc is not only water and dust resistant, but also able to withstand significant changes in temperature and humidity. Sony and Panasonic say the Archival Disc will have "inter-generational compatibility between different formats", so the data on the discs can be read as the format evolves, but of course this claim remains to be seen.

In the future, the companies are hoping to increase the capacity of Archival Discs from 300 GB up to 500 GB and 1 TB through inter symbol interface cancelation technology and multi-level recording technology respectively. Archival Discs aren't meant to replace Blu-rays, but they will be promoted in the professional space as an "effective solution for protecting valuable data into the future".

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