Jon Galloway

Atlas is an AJAX system for use with ASP.NET. Here are a few interesting notes from the Atlas session if, like me, you're generally aware of Atlas but haven't really dug into it that much.

Two client side script formats

In addition to Javascript, Atlas supports a new script type: Text/XML. XML is not a known script type, so it's ignored by browsers. The Atlas client side script parses it and converts it to standard Javascript. There are a few advantage`s to this approach:

• This allows you to program using declarative markup rather than wiring things up in code. This is similar to HTML or SQL - you describe what you want done, not how to do it. The Atlas runtime takes care of the details of turning your specifications into working script.
• XML style markup will allow for designer tools to edit the Atlas script; this would be much more difficult with Javascript.
• This is easier for the framework to support since it can use standard XML output systems.

You can see some sample code and read more about it on Nikhil's blog.

HTML / Javascript separation

AJAX functionality is activated through CSS classes rather than directly calling Javascript functions from HTML elements via event attributes such as "onclick". This clearly separates the display behavior (CSS and Javascript) from the content (HTML). I've been a fan of this markups based behavior  approach for a while, for both practical and philosophical reasons.

The practical advantages parallel the advantages of n-tier software design and semantic web design - clear separation of responsibilities yields simplicity, which pays of in the maintenance and upgrade phases. This clear separation also allows for gracefully degrading if, for instance, Javascript isn't supported on the user's platform.

The philosophical benefit is similar - HTML should describe content, and CSS / Javascript should describe behavior. The practical benefits above naturally fall out when things are structured correctly.

Ready for Prime Time?

The obvious disclaimer here: I haven't used Atlas. I spoke to two ASP.NET developers who have done some pretty intense AJAX coding on ASP.NET who have used Atlas, and they told me that it works great for simpler projects but didn't work great for them in actual projects. One person told me that the UpdatePanel control only worked in ASP.NET pages, not user or server controls due to the control event order. I got the impression that it's advancing very rapidly, but is still a little difficult to use in actual project circumstances.

Now, as I said, these are second hand accounts. I'm only passing them along to present balanced coverage and relay some real world impressions.

Some other random notes I jotted down: