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Ajax: A New Approach to Web Applications

If anything about current interaction design can be called “glamorous,” it’s creating Web applications. After all, when was the last time you heard someone rave about the interaction design of a product that wasn’t on the Web? (Okay, besides the iPod.) All the cool, innovative new projects are online.

Despite this, Web interaction designers can’t help but feel a little envious of our colleagues who create desktop software. Desktop applications have a richness and responsiveness that has seemed out of reach on the Web. The same simplicity that enabled the Web’s rapid proliferation also creates a gap between the experiences we can provide and the experiences users can get from a desktop application.
That gap is closing. Take a look at Google Suggest. Watch the way the suggested terms update as you type, almost instantly. Now look at Google Maps. Zoom in. Use your cursor to grab the map and scroll around a bit. Again, everything happens almost instantly, with no waiting for pages to reload.

Google Suggest and Google Maps are two examples of a new approach to web applications that we at Adaptive Path have been calling Ajax. The name is shorthand for Asynchronous JavaScript + XML, and it represents a fundamental shift in what’s possible on the Web.
Defining Ajax
Ajax isn’t a technology. It’s really several technologies, each flourishing in its own right, coming together in powerful new ways. Ajax incorporates:

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

The classic web application model works like this: Most user actions in the interface trigger an HTTP request back to a web server. The server does some processing — retrieving data, crunching numbers, talking to various legacy systems — and then returns an HTML page to the client. It’s a model adapted from the Web’s original use as a hypertext medium, but as fans of The Elements of User Experience know, what makes the Web good for hypertext doesn’t necessarily make it good for software applications.

This approach makes a lot of technical sense, but it doesn’t make for a great user experience. While the server is doing its thing, what’s the user doing? That’s right, waiting. And at every step in a task, the user waits some more.

Obviously, if we were designing the Web from scratch for applications, we wouldn’t make users wait around. Once an interface is loaded, why should the user interaction come to a halt every time the application needs something from the server? In fact, why should the user see the application go to the server at all?
How Ajax is Different
An Ajax application eliminates the start-stop-start-stop nature of interaction on the Web by introducing an intermediary — an Ajax engine — between the user and the server. It seems like adding a layer to the application would make it less responsive, but the opposite is true.

Instead of loading a webpage, at the start of the session, the browser loads an Ajax engine — written in JavaScript and usually tucked away in a hidden frame. This engine is responsible for both rendering the interface the user sees and communicating with the server on the user’s behalf. The Ajax engine allows the user’s interaction with the application to happen asynchronously — independent of communication with the server. So the user is never staring at a blank browser window and an hourglass icon, waiting around for the server to do something.

Every user action that normally would generate an HTTP request takes the form of a JavaScript call to the Ajax engine instead. 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.

Who’s Using Ajax

Google is making a huge investment in developing the Ajax approach. All of the major products Google has introduced over the last year — Orkut, Gmail, the latest beta version of Google Groups, Google Suggest, and Google Maps — are Ajax applications. (For more on the technical nuts and bolts of these Ajax implementations, check out these excellent analyses of Gmail, Google Suggest, and Google Maps.) Others are following suit: many of the features that people love in Flickr depend on Ajax, and Amazon’s search engine applies similar techniques.

These projects demonstrate that Ajax is not only technically sound, but also practical for real-world applications. This isn’t another technology that only works in a laboratory. And Ajax applications can be any size, from the very simple, single-function Google Suggest to the very complex and sophisticated Google Maps.

At Adaptive Path, we’ve been doing our own work with Ajax over the last several months, and we’re realizing we’ve only scratched the surface of the rich interaction and responsiveness that Ajax applications can provide. Ajax is an important development for Web applications, and its importance is only going to grow. And because there are so many developers out there who already know how to use these technologies, we expect to see many more organizations following Google’s lead in reaping the competitive advantage Ajax provides.

Moving Forward

The biggest challenges in creating Ajax applications are not technical. The core Ajax technologies are mature, stable, and well understood. Instead, the challenges are for the designers of these applications: to forget what we think we know about the limitations of the Web, and begin to imagine a wider, richer range of possibilities.

It’s going to be fun.

Ajax Q&A

March 13, 2005: Since we first published Jesse’s essay, we’ve received an enormous amount of correspondence from readers with questions about Ajax. In this Q&A, Jesse responds to some of the most common queries.

Q. Did Adaptive Path invent Ajax? Did Google? Did Adaptive Path help build Google’s Ajax applications?

A. Neither Adaptive Path nor Google invented Ajax. Google’s recent products are simply the highest-profile examples of Ajax applications. Adaptive Path was not involved in the development of Google’s Ajax applications, but we have been doing Ajax work for some of our other clients.

Q. Is Adaptive Path selling Ajax components or trademarking the name? Where can I download it?

A. Ajax isn’t something you can download. It’s an approach — a way of thinking about the architecture of web applications using certain technologies. Neither the Ajax name nor the approach are proprietary to Adaptive Path.

Q. Is Ajax just another name for XMLHttpRequest?

A. No. XMLHttpRequest is only part of the Ajax equation. XMLHttpRequest is the technical component that makes the asynchronous server communication possible; Ajax is our name for the overall approach described in the article, which relies not only on XMLHttpRequest, but on CSS, DOM, and other technologies.

Q. Why did you feel the need to give this a name?

A. I needed something shorter than “Asynchronous JavaScript+CSS+DOM+XMLHttpRequest” to use when discussing this approach with clients.

Q. Techniques for asynchronous server communication have been around for years. What makes Ajax a “new” approach?

A. What’s new is the prominent use of these techniques in real-world applications to change the fundamental interaction model of the Web. Ajax is taking hold now because these technologies and the industry’s understanding of how to deploy them most effectively have taken time to develop.

Q. Is Ajax a technology platform or is it an architectural style?

A. It’s both. Ajax is a set of technologies being used together in a particular way.

Q. What kinds of applications is Ajax best suited for?

A. We don’t know yet. Because this is a relatively new approach, our understanding of where Ajax can best be applied is still in its infancy. Sometimes the traditional web application model is the most appropriate solution to a problem.

Q. Does this mean Adaptive Path is anti-Flash?

A. Not at all. Macromedia is an Adaptive Path client, and we’ve long been supporters of Flash technology. As Ajax matures, we expect that sometimes Ajax will be the better solution to a particular problem, and sometimes Flash will be the better solution. We’re also interested in exploring ways the technologies can be mixed (as in the case of Flickr, which uses both).

Q. Does Ajax have significant accessibility or browser compatibility limitations? Do Ajax applications break the back button? Is Ajax compatible with REST? Are there security considerations with Ajax development? Can Ajax applications be made to work for users who have JavaScript turned off?

A. The answer to all of these questions is “maybe”. Many developers are already working on ways to address these concerns. We think there’s more work to be done to determine all the limitations of Ajax, and we expect the Ajax development community to uncover more issues like these along the way.

Q. Some of the Google examples you cite don’t use XML at all. Do I have to use XML and/or XSLT in an Ajax application?

A. No. XML is the most fully-developed means of getting data in and out of an Ajax client, but there’s no reason you couldn’t accomplish the same effects using a technology like JavaScript Object Notation or any similar means of structuring data for interchange.

Q. Are Ajax applications easier to develop than traditional web applications?

A. Not necessarily. Ajax applications inevitably involve running complex JavaScript code on the client. Making that complex code efficient and bug-free is not a task to be taken lightly, and better development tools and frameworks will be needed to help us meet that challenge.

Q. Do Ajax applications always deliver a better experience than traditional web applications?

A. Not necessarily. Ajax gives interaction designers more flexibility. However, the more power we have, the more caution we must use in exercising it. We must be careful to use Ajax to enhance the user experience of our applications, not degrade it.

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Jesse James Garrett is the Director of User Experience Strategy and a founder of Adaptive Path. He is the author of the widely-referenced book The Elements of User Experience.

Other essays by Jesse James Garrett include The Nine Pillars of Successful Web Teams and Six Design Lessons From the Apple Store.

(Collected from Adaptive Path)

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.NET Framework 3.5

.NET Framework (NetFx or Fx) version 3.5 has two elements to it that must be understood: the green bits and the red bits. The original references to this term are on old blog posts by Soma and Jason. Compared to those two blog entries I have the advantage of 13 months of hindsight :-) , so I will provide here the details behind those descriptions in my own words starting with my own slide:

.NET Framework 3.5

.NET Framework 3.5

When we say red bits, those are Framework bits that exist in RTM today i.e. NetFx v2.0 and NetFx v3.0.

NetFx v3.5 includes updates for those two existing frameworks. However, those updates are not a whole bunch of new features or changes, but in reality a service pack with predominantly bug fixes and perf improvements. So to revisit the terminology: Fx 3.5 includes v2.0 SP1 and v3.0 SP1. Like with all service packs, there should be nothing in there that could break your application. Having said that, if a bug is fixed in the SP and your code was taking advantage of that bug, then your code will break of course. To be absolutely clear, this is an in-place upgrade to v2 and v3, not a side-by-side story at the framework/clr level. I will not focus anymore on the Service Pack (red bits) improvements in Fx 3.5. If you are interested in that you may wish to read my previous blog posts here, here, here and here.

When we say green bits, we mean brand new assemblies with brand new types in them. These are simply adding to the .NET Framework (not changing or removing) just like Fx 3.0 was simply adding to v2.0 without changing existing assemblies and without changing the CLR engine. It is here where you find the brand new stuff to talk about. In Beta 1, the list of new assemblies (green bits) is:

1. System.Data.Linq.dll – The implementation for LINQ to SQL.

2. System.Xml.Linq.dll – The implementation for LINQ to XML.

3. System.AddIn.dll, System.AddIn.Contract.dll – New AddIn (plug-in) model.

4. System.Net.dll – Peer to Peer APIs.

5. System.DirectoryServices.AccountManagement.dll – Wrapper for Active Directory APIs.

6. System.Management.Instrumentation.dll – WMI 2.0 managed provider (combined with System.Management namespace in System.Core.dll).

7. System.WorkflowServices.dll and System.ServiceModel.Web.dll – WF and WCF enhancements (for more on WF + WCF in v3.5 follow links from here).

8. System.Web.Extensions.dll – The implementation for ASP.NET AJAX (for more web enhancements, follow links from here) plus also the implementation of Client Application Services and the three ASP.NET 3.5 controls.

9. System.Core.dll – In addition to the LINQ to Objects implementation, this assembly includes the following: HashSet, TimeZoneInfo, Pipes, ReaderWriteLockSlim, System.Security.*, System.Diagnostics.Eventing.* and System.Diagnostics.PerformanceData.

Collected from Daniel Moth blog


UTF-8 Encoding

In working on a web-based application that needed to support Netscape Communicator 4.x+ and Microsoft Internet Explorer 5.x+, I discovered that the older versions of these browsers had poor support for UTF8 encoding. I needed to find a way to make form field entries URL-safe and also needed to support multiple languages. The JavaScript escape() function fixes ASCII characters that are not valid for use in URLs, but does not handle unicode characters well. To make matters worse, there were browser incompatibilities: using escape() in IE would generate a new string that looked like %unnnn, where n is a hexadecimal digit. The correct encoding should follow RFC 2279 and be a set of hexadecimal digit pairs like %nn%nn. Netscape 4 would just treat the characters as ASCII, which would result in lost accents and umlauts.

The encodeURIComponent() function introduced in IE5.5, Netscape 6, and Mozilla does exactly what is needed. However, since the function is unavailable in Netscape 4.x and IE5, a different solution is needed. All JavaScript strings are unicode, so I expected that it would be possible to properly encode them. Thankfully, someone saw my plea for help and sent me some helpful example code.

I have faced this problem. When using ajax jquery, even I have set the contentType is "application/json;charset=utf-8" it still not working for accented language (like Vietnamese). After searching, I have realized that we have to use this method encodeURIComponent() to encode unicode characters before submitting to server. So I took note it here with a hope that it is useful for ones who may face same problem as mine.

Collected from

Filed under: AJAX, ASP.NET, JQuery No Comments