What is Universal Description, Discovery, and Integration (UDDI)

Most common problem for many businesses is to identify best way to reach their customers and partners with appropriate information about thier services and products.
UDDI empowers by providing a standardised approach which allows copanies to advertise both businesses and technical aspects of their services.

Actually this is achieved by having an informational framework that describes and classifies the organizations, its services and technical details about various interfaces of web services.
This framework also proves discovery of interfaces and web-servicesof a particular type, classification or function. UDDI can considered as Yellow pages for web serives. Most of the registered UDDIs can be found at

http://uddi.ibm.com
http://uddi.microsoft.com

What is Web Services Description Language (WSDL)

WSDL is a document written in XML that describesfour critical peices of information:

1. Interface information for describing all publically available functions
2. Data-Type Information for all  message requests and responses.
3. Binding information about protocol used for transportation.
4. Address Information for locating appropriate service.


WSDL is a mechanism by which others know how to intercat with a particular service.
It gives the information about the place where service resides, what a service can do and how to invoke that particular web service.
WSDL is oftenly used in Combination with SOAP and XML to provide Web Service over Internet.
WSDL represents a cornerstone of web service architecture because it provides a common language for describing services and platform for automatically integrating all these services.


AN EXAMPLE OF WSDL looks like:

What are Web Services ???

Web Services are next level of Web applications. Web Services expose internal data and interfaces with other programs. These are similar to Application Programing Interfaces (APIs), a Web Application can use multiple web services and these can be shared between multiple Companies.

Self contained pieces of functionality that can be published, located and invoked on internet, Web Servuces can expose business functionality, services and data over web using automated interfaces.All such interfaces allow different organizatons to find functionality they require on runtime.


For basic pillars of Web Services are :


1) eXtensible Markup Language (XML)

2) Simple Object Access Protocal (SOAP)

3) Web Services Description Language (WSDL)

4) Universal Description, Discovery, and Integration (UDDI)

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HTTP Status Code : 1XX Informational

1xx Informational

This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. Since HTTP/1.0 did not define any 1xx status codes

100 Continue

This means that the server has received the request headers, and that the client should proceed to send the request body (in the case of a request for which a body needs to be sent; for example, a POST request). If the request body is large, sending it to a server when a request has already been rejected based upon inappropriate headers is inefficient. To have a server check if the request could be accepted based on the request's headers alone, a client must send Expect: 100-continue as a header in its initial request

101 Switching Protocols

This means the requestor has asked the server to switch protocols and the server is acknowledging that it will do so.

102 Processing

HTTP Status Codes : 2XX for Success

2xx Success

This class of status code indicates that the client's request was successfully received, understood, and accepted

200 OK

Standard response for successful HTTP requests. The actual response will depend on the request method used. In a GET request, the response will contain an entity corresponding to the requested resource. In a POST request the response will contain an entity describing or containing the result of the action.

201 Created

The request has been fulfilled and resulted in a new resource being created.

202 Accepted

The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually be acted upon, as it might be disallowed when processing actually takes place.

203 Non-Authoritative Information

The server successfully processed the request, but is returning information that may be from another source.

204 No Content

The server successfully processed the request, but is not returning any content.

205 Reset Content

The server successfully processed the request, but is not returning any content. Unlike a 204 response, this response requires that the requestor reset the document view.

206 Partial Content

The server is serving only part of the resource due to a range header sent by the client. This is used by tools like wget to enable resuming of interrupted downloads, or split a download into multiple simultaneous streams.

207 Multi-statuses

The message body that follows is an XML message and can contain a number of separate response codes, depending on how many sub-requests were made.

What is AJAX

Ajax, sometimes written as AJAX (shorthand for asynchronous JavaScript and XML), is a group of interrelated web development techniques used on the client-side to create interactive web applications or rich Internet applications.

With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. The use of Ajax has led to an increase in interactive animation on web pages and better quality of Web services thanks to the asynchronous mode. Data is retrieved using the XMLHttpRequest object. Despite the name, the use of JavaScript and XML is not actually required, nor do the requests need to be asynchronous.

Advantages

* In many cases, related pages on a website consist of much content that is common between them. Using traditional methods, that content would have to be reloaded on every request. However, using Ajax, a web application can request only the content that needs to be updated, thus drastically reducing bandwidth usage and load time.

* The use of asynchronous requests allows the client's Web browser UI to be more interactive and to respond quickly to inputs, and sections of pages can also be reloaded individually. Users may perceive the application to be faster or more responsive, even if the application has not changed on the server side.

* The use of Ajax can reduce connections to the server, since scripts and style sheets only have to be requested once.

* State can be maintained throughout a Web site. JavaScript variables will persist because the main container page need not be reloaded.

Disadvantages

* Pages dynamically created using successive Ajax requests do not automatically register themselves with the browser's history engine, so clicking the browser's "back" button may not return the user to an earlier state of the Ajax-enabled page, but may instead return them to the last full page visited before it. Workarounds include the use of invisible IFrames to trigger changes in the browser's history and changing the anchor portion of the URL (following a #) when AJAX is run and monitoring it for changes.

* Dynamic web page updates also make it difficult for a user to bookmark a particular state of the application. Solutions to this problem exist, many of which use the URL fragment identifier (the portion of a URL after the '#') to keep track of, and allow users to return to, the application in a given state.

* Because most web crawlers do not execute JavaScript code, web applications should provide an alternative means of accessing the content that would normally be retrieved with Ajax, to allow search engines to index it.

* Any user whose browser does not support Ajax or JavaScript, or simply has JavaScript disabled, will not be able to use its functionality. Similarly, devices such as mobile phones, PDAs, and screen readers may not have support for JavaScript or the XMLHttpRequest object.[citation needed] Also, screen readers that are able to use Ajax may still not be able to properly read the dynamically generated content. The only way to let the user carry out functionality is to fall back to non-JavaScript methods. This can be achieved by making sure links and forms can be resolved properly and rely not solely on Ajax. In JavaScript, form submission could then be halted with "return false".

* The same origin policy prevents some Ajax techniques from being used across domains, although the W3C has a draft that would enable this functionality.

* Ajax opens up another attack vector for malicious code that web developers might not fully test for.