AJAX- Tech and Technology
It is technology for a new wave of browser-based apps that will replace most standard desktop apps. Another benefit is that they don't require an installation process the way packaged software does. And in this software model, fixes and upgrades can be made at any time, on the server, and without the user needing to do anything.
The Ajax technique uses a combination of:
|XHTML (or HTML ), CSS , for marking up and styling information. -
||XML is commonly used as the format for transferring data back from the server, although any format will work, including preformatted HTML, plain text, JSON and even EBML .
||Like DHTML , LAMP , or SPA , Ajax is not a technology in itself, but a term that refers to the use of a group of technologies together.
||Remote Scripting Frameworks such as ARSCIF surfaced in not long before Microsoft introduced Callbacks in ASP.NET
||Since XMLHttpRequest is now implemented across the majority of browsers in use, alternative techniques are used infrequently. However, they are still used where wide compatibility, small implementation, or cross-site access are required. One alternative, the SVGT protocol , employs a persistent connection for continuous exchange between browser and service.
||Some early articles promoting Remote Scripting techniques:
||Microsoft Internet Developer Magazine 1998
||ScottAndrew's XML-RPC example 2001
||Apple Developer Connection 2002
||Using the XML HTTP Request object 2002-2006
|| Pros, cons and criticism
||Ajax applications are mainly executed on the user's machine, by manipulating the current page within their browser using document object model methods. Ajax can be used for a multitude of tasks such as updating or deleting records;expanding web forms; returning simple search queries; or editing category trees -- all without the requirement to fetch a full page of HTML each time a change is made. Generally only small requests are required to be sent to the server, and relatively short responses are sent back. This permits the development of more interactive applications featuring more responsive user interfaces due to the use of DHTML techniques.
||Ajax applications use well-documented features present in all major browsers on most existing platforms. Though this situation could feasibly change in the future, at the moment, Ajax applications are effectively cross-platform.
||While the Ajax platform is more restricted than the Java platform, current Ajax applications effectively fill part of the one-time niche of Java applets : extending the browser with lightweight mini-applications.
|| Cons and criticism
|| Usability criticisms
||One major complaint voiced against the use of Ajax in web applications is that it might easily break the expected behavior of the browser's back button. The different expectations between returning to a page which has been modified dynamically versus the return to a previous static page might be a subtle one. Users generally expect that clicking the back button in web applications will undo their last state change, and in Ajax applications this might not be the case. Developers have implemented various solutions to this problem, most of which revolve around creating or using invisible IFRAMEs to invoke changes that populate the history used by a browser's back button. Google Maps , for example, performs searches in an invisible IFRAME and then pulls results back into an element on the visible web page; it is possible to track user behaviour via callbacks which are called whenever the back button is pressed, restoring the application state that existed at the time.
|| Response-time concerns
||Network latency — or the interval between user request and server response — needs to be considered carefully during Ajax development. Without clear feedback to the user 4 , smart preloading of data 5 , and proper handling of the XMLHttpRequest object 6 users might experience delay in the interface of the web application, something which users might not expect or understand. 7 The use of visual feedback to alert the user of background activity and/or preloading of content and data are often suggested solutions to these latency issues.
||In general the potential impact of latency has not been "solved" by any of the Public Domain AJAX toolkits and frameworks available today, such as the effect of latency variance over time 8 .
|| Name issues
||There have been some critics of the term Ajax, claiming that Adaptive Path (the consulting firm that coined the term 9 ) or other proponents are using it as a marketing vehicle for previously-used techniques 10
||Using Ajax technologies in web applications provides many challenges for developers interested in adhering to WAI
accessibility guidelines. Developers need to provide fallback options for users on other platforms or browsers, as most methods of Ajax implementation rely on features only present in desktop graphical browsers.
||Web developers use Ajax in some instances to provide content only to specific portions of a web page, allowing data manipulation without incurring the cost of re-rendering the entire page in the web browser. Non-Ajax users would optimally continue to load and manipulate the whole page as a fallback, allowing the developers to preserve the experience of users in non-Ajax environments (including all relevant accessibility concerns) while giving those with capable browsers a much more responsive experience.
|| Browsers that support Ajax
||Note that this is a general list, and support of Ajax applications will depend on the features the browser supports.
Internet Explorer version 5.0 and above, and browsers based on it (Mac OS versions not supported
||Gecko -based browsers like Mozilla , Mozilla Firefox , SeaMonkey , Camino , Flock , Epiphany , Galeon and Netscape version 7.1 and above -
||Opera browsers version 8.0 and above, including Opera Mobile Browser version 8.0 and above
|| Browsers that do not support Ajax
||This is a list of browsers that definitely do not support Ajax
||JSON, AJAX Without XML
||Single Page Application
||Ajax: A New Approach to Web Applications , by Jesse James Garrett . The original article which coined the term.
||Why Ajax Matters Now by Jesse James Garrett .
||Weighing the Alternatives How Ajax stacks up against competing RIA approaches.
||Why IFrame based AJAX is better than using XMLHttpRequest
||Ajax Write - Online word processor ajaxWrite is a Web-delivered word processor. One of the future applications will no longer live on your hard drive.
||AJAX:Getting Started by Mozilla Developer Center.
||Building an Ajax page With GET, POST, TEXT, XML examples.
||Dynamic HTML and XML: The XMLHTTPRequest Object by Apple .
||Cross-browser Ajax Tutorial using the Sarissa library.
||Mastering Ajax Introduction to Ajax (four parts).
||Ajax Freaks provide you with information to use while learning or developing AJAX. If you need AJAX Help or you would like to provide AJAX Help to other developers, you are in the right place.
||Ajaxian Ajax and develper articles.
||A cross-browser DHTML table Bypass the limitations of HTML with this custom Web control
|| Google Code - Source Code from Google
||Google APIS Google API
||AJAX Feed API Documentation AJAX Feed API Documentation
||AJAX Search API Documentation AJAX Search API Documentation
||The Slide Show Control The Slide Show Control
||The iTunes Bar The iTunes Bar
||dynamicfeed The dynamic feed RSS Horizontal Mode
||Google Developers Feed Developer Guide
||Ajax General Information and Updated References
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