XForms
XForms recently reached the W3C's Candidate Recommendation status—and you need to know about it—because XForms isn't a form description language, it's a language for describing applications in a platform-independent way. Best of all, it integrates easily with technologies you already know, such as XHTML, XPath, SVG, and CSS.
If you want to know more about XForms, Devx has a great article on this new language.
A question is about XAML: is it a Microsoft interpretation of XForm or something else ?!?
A question is about XAML: is it a Microsoft interpretation of XForm or something else ?!?