Clicks & Notes

adaptive path - ajax: a new approach to web applications

• “Ajax” (shorthand for “Asynchronous JavaScript + XML") is a way to make web applications more responsive to user interaction
• traditional web applications rely on communication between a user and a web server via HTTP, which result in a “start-stop-start-stop” type of interaction:
  • user sends a request to the server
  • the server processes the request
  • the server returns a(nother) web page back to the user
  • repeat…
• an Ajax “engine"– written in JavaScript, and loaded at the start of a user session – can instead act as an intermediary between the user and server:
  

  Any response to a user action that doesn’t require a trip back to the server — such as simple data validation, editing data in memory, and even some navigation — the engine handles on its own

  If the engine needs something from the server in order to respond — if it’s submitting data for processing, loading additional interface code, or retrieving new data — the engine makes those requests asynchronously, usually using XML, without stalling a user’s interaction with the application.

• Ajax is not a new technology in and of itself; it incorporates existing web technologies:
  

  • standards-based presentation using XHTML and CSS;
  • dynamic display and interaction using the Document Object Model;
  • data interchange and manipulation using XML and XSLT;
  • asynchronous data retrieval using XMLHttpRequest;
  • and JavaScript binding everything together.

• current online applications using Ajax include the various Google products, Flickr and A9.com