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Post: #1

Ajax, shorthand for Asynchronous JavaScript and XML, is a web development technique for creating interactive web applications. The intent is to make web pages feel more responsive by exchanging small amounts of data with the server behind the scenes, so that the entire web page does not have to be reloaded each time the user makes a change. This is meant to increase the web page s interactivity, speed, and usability.

The Ajax technique uses a combination of:
XHTML (or HTML) and CSS, for marking up and styling information.
The DOM accessed with a client-side scripting language, especially ECMAScript implementations such as JavaScript and JScript, to dynamically display and interact with the information presented.
The XMLHttpRequest object to exchange data asynchronously with the web server. In some Ajax frameworks and in certain situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server.

XML is sometimes used as the format for transferring data between the server and client, although any format will work, including preformatted HTML, plain text, JSON and even EBML.
Like DHTML, LAMP and SPA, Ajax is not a technology in itself, but a term that refers to the use of a group of technologies together.
Post: #2

To create custom dynamic web applications a programmer must utilize Ajax. Ajax is a group of technologies that provide asynchronous two-way communication between a server and the web browser. Asynchronous communication allows the user to continue to browse the web page as sections of it are being loaded. This also allows the page to display new and updated information with out refreshing the page.Ajax development has exploded in recent years as companies have found customers prefer pages developed with it. ESPN uses Ajax extensively on their website to refresh scores and provide news headlines without the user having to update the page.
Creating an Ajax request requires three sections of code, the first section is writing in HTML, the second writing in JavaScript and the third is a server script writing PHP. Each section of code provides a different portion of the Ajax request, if the request is missing any of the sections it will fail. While Ajax is good for many scenarios a programmer must carefully examine its use to prevent problems from arising.
AJAX is a relatively new method to create rich internet applications with responsive interfaces that allow the designer to take a lot of the tedium out of using web-based mediums for day-to-day data interaction. The scope of this paper will be to provide information about what AJAX is and what it does, when it should and shouldn’t be used and what the future looks like for AJAX in comparison to the present and future alternatives. This will help developers determine the value of using AJAX in their projects and provide information about the proper use of this technology. This report will assume a basic knowledge with web forms and the design of web applications.
AJAX is an acronym for Asynchronous JavaScript and XML. It is not a technology in itself, but rather a suite of technologies. The combination of JavaScript and XML allows for a responsive user interface. It requires more development time than a traditional web solution; however a well-designed AJAX user interface makes the traditional form-based web application seem almost archaic.
The technologies powering the internet are changing at an accelerated rate; one of these technologies is Ajax. Ajax or Asynchronous JavaScript and XML are a group of technologies that provide a rich web development platform. Jesse James Garrett introduced the term Ajax in February of 2005 to describe a new method of programming using readily available technologies. Ajax requires four distinct components to provide a rich user interface. The components are JavaScript, XML, HTML, and CSS.
Ajax is unique because it allows for the creation of desktop like applications in a web environment. Typically a “desktop” application is very responsive and can have sections of the program change without refreshing the entire screen. This occurs because the program is running on the local machine. Web applications usually run thru an internet browser like Microsoft Internet Explorer or Mozilla Firefox. These applications are usually slower because they require the server to process each request. Most web applications require the entire webpage to be processed at once. This means when a user clicks on a link in a webpage the whole page will be changed. With Ajax a user can click on a link and have a section of the page recreated for them without changing the whole page. This removes a portion of the load from the server because it only has to parse a section of the page rather than the whole page.
What is AJAX and what does it do?
As mentioned in the introduction, AJAX is a suite of technologies used to create rich internet applications. It uses JavaScript to gather and show data to the user. It uses XML transmitted either in the XMLHTTPRequest or IFrame objects to communicate with the server. Together they allow the user to do a lot of things interactively with one web page. The diagram illustrates on which side of the data transaction XML and JavaScript function.
As opposed to traditional form-based interaction, in an AJAX application, JavaScript provides a lot of the interaction. While elements of web-forms are often used, in well-designed AJAX, JavaScript becomes the medium for interaction and the web page only provides the layout for the data and the way it will be displayed. JavaScript is in charge of the input and output events and displaying the data associated with those events. This allows one web page to display and manipulate a lot of data without having to be reloaded.
While JavaScript can manage the user interface, it cannot communicate with the server. This is where XML comes into play. This paper will discuss XML but any method of conveying data can be used if the situation requires it. XML serves as the communication between the web page and the server. This makes a compact response object because the server only has to send an XML object representing the data that will be displayed in the web page already in the browser. By creating a smaller response object and putting some of the processing associated with display on the client computer, resources from the server are saved. Finally, since the client doesn’t need to load a new page, the data is displayed much quicker, creating a much faster interface that is much more enriching for the user.
It’s not hard to see how many applications this would have. A great example would be a form that allows users to look at their email. In the traditional web form model, a user would have to view a new web page every time they wanted to cycle to a new email. Using an AJAX web application, the user could cycle through emails without ever having to load a new web page. This is an example of a simple AJAX application although it could go so far as to implement a menu to select which email to view, a way to create and send emails, and a method of instantly notifying a user of new emails into the same web page, never having to be refreshed. Obviously, this would create a faster and more responsive web experience.

Even though Ajax wasn’t formally defined until February of 2005 the first Ajax type web application was released in 2000 by Microsoft for use with Outlook. Microsoft was looking to create a web based version of its popular email client that did not require the page to be refreshed to notify the user a new email had arrived. Microsoft created the XMLHttpRequest object which became the basis for Ajax traffic. The XMLHttpRequest allows a client computer to call a webpage in the background without interfering with the user. This type of transfer is called asynchronous because it passively waits for the server to respond. This is the first component in Ajax and is usually called thru JavaScript.
Using the XMLHttpRequest data can be gathered from the server. To update the webpage to show this new data Dynamic HTML must be used. Dynamic HTML uses CSS, HTML and JavaScript to rewrite sections of the webpage code at the browser instead of regenerating the page on the server.
The term Ajax became widely known after the release of Google Maps and Google Suggest. These products showed flexibility never before seen in a web application and thus spurred developers to make new and innovative applications.
A time and a place…
With all of this power, why not use AJAX for everything a webpage does? Since all AJAX provides is a method of synchronizing and transferring data on request from the user and then manipulating it into the display, it shouldn’t be used for everything. While it may be tempting to create a web site that uses AJAX to provide on-the-fly search functionality and customizable navigation, AJAX development takes a lot of time, and the charm it provides will quickly wear off. Here are some situations where the development of an AJAX solution will provide the maximum return from development costs.
Forms: There is nothing more tedious than having to use the traditional web-form method for data entry. By applying AJAX to web forms, an amazing amount of functionality is added. Imagine being able to create a Windows application style interface to receive information from users on the web. When compared to a standard web interface, this seems much better. AJAX in forms has an obvious use anywhere multiple instances of the same data type will be received or displayed. It can also be used where modifying information will change information somewhere else to provide real-time updates.
Rapid Interaction: AJAX allows a web page to be used to create rapid interaction with the user. AJAX can make instant messaging on a web page a reality. AJAX can be used to allow a web page to serve as an event-based alarm, such as a stock ticker that warns the user when a price is reached. AJAX can be used in any situation where a browser is typically auto-refreshed which is another way AJAX moves the functionality in creating web applications closer to the freedom had when creating Windows applications.
Avoiding Refreshing: AJAX should be used in any situation that requires a lot of browser refreshing. Loading large lists for several small manipulations or working through a long tree view on a forum are tedious examples of situations where traditional web solutions spend a lot of time refreshing. Filling out small request or voting form on the side of a larger feature is so slow and distracting users avoid doing it. AJAX provides an elegant solution to all of these problems by being able completely avoid browser refreshing.
Auto Complete: This is tricky situation. AJAX can provide a great solution here when it provides auto completion of things that are similar between many users or a situation where users would use different language to describe the same thing. However, the time spent developing something like this for a website may just end up overlapping functionality already provided by most major browsers. If done correctly however, using AJAX to provide a well placed auto completion text box is a great idea, the key is to make sure that major browser’s auto-complete functionality isn’t duplicated and that the auto-completion being provided is worth the time to develop it.
AJAX has a fairly slow development time and it is in a developer’s best interest to use it only where it will provide a benefit that is worth the extra development time. For example, using AJAX to manage the navigation on a website is overkill. Using the DOM, CSS and XHTML is an easier and faster way to develop this. As outlined before, typically AJAX shouldn’t be used to provide the shape of the interface, but should be used to handle the interaction between the Client and the Server with the web page as the middle ground.
Post: #3


What is Ajax

Ajax (Asynchronous JavaScript and XML) is a method of building interactive applications for the Web that process user requests immediately.”

Ajax combines several programming tools including JavaScript, dynamic HTML (DHTML), Extensible Markup Language (XML), cascading style sheets (CSS), the Document Object Model (DOM), and the Microsoft object, XMLHttpRequest

Ajax works as Intermediary

The Ajax engine works within the Web browser (through JavaScript and the DOM) to render the Web application and handle any requests that the customer might have of the Web server.

Ajax is a way of developing web applications that combines

.XHTML and CSS standards based presentation

.Interaction with the page through the DOM

.Data interchange with XML and XSLT

.Asynchronous data retrieval with XMLHttpRequest

.JavaScript to tie it all together

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