Raible Designs

User Interface Schema Definitions

On my current project, we're developing a "designer" tool that allows users to build forms in their browser. These forms are displayed in various channels (e.g. web, mobile, sms) to capture data and make decisions based on user input.

When I joined the project, it was in a proof-of-concept phase and the form definitions created where serialized as XML (using JAXB) with element names that seemed logical. Now that we're moving the PoC to production mode, we're thinking it might be better to change our form definitions to leverage something that's more "industry standard". If nothing else, it'll help with marketing. ;-)

This week, I was tasked with doing research on "existing user interface schema definitions". I'm writing this post to see if there's any major specifications I'm missing. I plan on providing my recommendation to my team on Monday. Here's what I've found so far:

• User Interface Markup Language (UIML): At 120 pages, the 4.0 spec seems very detailed. I'm not sure we'd use all of it, but it's interesting how the spec allows you to describe the initial tree structure (<structure>) and to dynamically modify its structure (<restructure>). It also has the notion of templates, which mirrors a similar concept we have in our application. Furthermore, it has VoiceXML support, which could be useful if we use call centers as a channel.
• USer Interface eXtensible Markup Language (UsiXML): I admit that I haven't read much of this specification -- mostly because the UIML spec seemed to cover most of what we needed (especially since we're most interested in describing forms). As far as a I can tell, the major difference between UsiXML is its being submitted to the W3C for standardization (according to Wikipedia), while UIML is being standardized by OASIS. Beyond that, I find it strange that UIML's spec is 120 pages and UsiXML is 121. Neither project seems to have any activity this year.
• Numerous others: including AAIML, AUIML, XIML, XUL, XAML and XForms. XForms seems like it may be the most logical if we're only interested in form layout and describing elements within them.

If all we're interested in is an XSD to define our forms, the most appealing specs have them: UIML, UsiXML and XForms. If activity is any sort of motivator for adoption, it's interesting to note that XForms 1.1 was submitted as a W3C recommendation a couple weeks ago (October 20, 2009).

If you've developed some sort of "form designer" tool that renders to multiple channels, I'd love to hear about your experience. Did you use some sort of industry standard to define your form elements, layout, etc. or did you come up with your own?