What you are essentially saying here is what drives me mad about the web. You are saying that a whole host of useful, and in some cases fundamental, UI components are simply not natively available to developers in the so-called web platform. Whilst desktop application developers merely have to click and drag fundamental components into their applications, web developers have to go through a whole process of deciding which library to use, trading off the weight of using more than one library or tolerating the often sub-par components available with their chosen library.

A great example is jQuery UI. I love jQuery and I'm sure the jQuery UI guys work very hard but given that jQuery was one of the later libraries to hit the mainstream and jQuery UI was even later, they are really struggling to provide fundamental components that behave reliably. Do I include the core code of another JS library merely to get access to one component?

It is realisations like this that make me laugh at the people who think the web is the future of applications. Native standardised UI components in browsers have not changed for a decade or more. Meanwhile Mozilla 'progresses' by constantly developing technology that will not ever be supported cross-browser such as canvas, SVG and so on. It's one of the reasons I've abandoned the web as an application platform. People can talk about Web 2.0 and "cloud" computing as much as they like however when core components are not available web applications are still a compromised joke. For years we've heard about stuff like xForms and so on. For years I've been doing 'the right thing' by designing to web standards. However those standards are pathetic in that they do not form a framework within which a web application framework with basic UI components is possible.

(From Alex: Profanities deleted. Keep your eye out for HTML 5, though. If I ever get back to working on it, you'll see some small improvements.)

About XForms, have a look at XSLTForms (http://www.agencexml.com/xsltforms).

It's a client side implementation based only on XSLT 1.0 and Javascript. That's why it's a cross-browser solution.

For web application, XRX (XForms-REST-XQuery) architecture is very interesting, don't you think ?

Isn't the problem of providing bandwidth to download a large js library partly solved by Google AJAX Libraries API? As the provision of consistent URLs allows client side caching of common code.