The "Presentation" Layer

What do people mean by the "view" or "presentation" layer? In a Web application, I gather that it means the "stuff" that runs in a browser; normally HTML, CSS, and JavaScript. Then add "stuff" that runs in browser plug-ins; like Flash and Silverlight.

Some say that you can include stuff that's hosted or runs on the server, that generates browser output, or processes browser input. That's probably about as far as you can stretch the "presentation layer". At some point you need to distinguish "presentation" from "business" and "data access" layers if you're following a model-view-controller design pattern.

My reason for raising this topic is because I've been reading and pondering about "rich" UI frameworks during the past week. More specifically, I've been looking at Prototype, YUI (Yahoo User Interface Components), GWT (Google Web Toolkit), dojo, Ext js, MooTools, and Open Laszlo. I've been talking with people who are getting into Adobe Flex & ActionScript.

I've been investigating whether to invest time into mastering one of the toolkits, or to continue along my current approach of pairing HTML with CSS and a modest amount of JavaScript.

I'm somewhat impressed with the UI widgets in Ext js. To the point that I got out the JavaScript tutorial and started learning a JavaScript notation called Object Literals, which are used extensively in Ext js & Prototype, and allow developers to define object properties and methods using an abbreviated syntax. Click http://www.radile.com/rdweb/temp/objects.html to see a example of using "Literals" to define an object containing three properties and a method that writes the property values to the screen.

If I were to adopt Ext js as a toolkit, I'd need to become proficient at writing code like that.

On the other hand, Joe Pluta keeps proclaiming that with EGL, you don't need to learn how to write presentation layer code. The workbench does it for you.

Any thoughts?

Thanks,

Nathan.