Building Mobile Applications with xH

Mark Birbeck

w: <http://www.formsPlayer.com/>

b: <http://internet-apps.blogspot.com/>

e: <mark.birbeck@gmail.com>

Mobile Ajax and mobile apps

Mobile Ajax is usually discussed in relation to widgets and scripting.
Want to look at it in relation to applications:
- Difficult to build enterprise applications that have a mobile element.
- High entry level--usually have to break out Java or C++.
- Want a standard interface to the various devices.

Why not create apps with standards?

Use xH to write the code.
Layer xH onto an Ajax backplane.
Extend backplane to allow access to device-specific features.
Now have declarative, 'unobtrusive' way to build mobile applications.

What is xH?

Combine standard mark-up languages to create a programming language.
This means that the same language can be used to build web apps, widgets and desktop apps.
More a set of guidelines than a new language.

xH languages

XHTML
RDFa
@role
XForms
XML Events
SMIL
SVG
XBL

xH languages

XHTML gives us the framework and the document.
RDFa and @role give us more information about the document.
XForms gives us data communication and management.
XML Events allows these language modules to communicate.
XHTML, XForms and SVG give us the user interface.
XBL allows us to hide the specifics of the UI, which means we can easily customise it.
SMIL allows us to animate the UI.

xH schemas make tools

By using schemas your favourite XML editor gets 'intellisense'.
Unusual to be able to validate code.
Based on XHTML Modularisation 1.1.
Modules have already been created for RDFa and @role, and modules are in progress for XForms.

xH extensions for apps

Use meta to specify parameters:

          <head>
            <meta name="width" content="200" />
            <meta name="height" content="200" />
            <meta name="opacity" content="75" />
          </head>

and XPointer-style URLs:

          http://myapp#meta(width=200,height=200,opacity=75)

Layer xH onto Ajax backplane

Backplane has standard 'components' that are common to many languages:

Submission module, which builds on XMLHttpRequest, but adds standard events, validation, multiple serialisations, and more.
Animation module which provides DOM access to SMIL.
And more. (Session tomorrow.)

Declarative Ajax, or 'Unobtrusive JavaScript'

Concept that is gaining ground, but no clear winner.

My proposal is that xH is a pretty good candidate.

Conclusion

Building mobile apps is difficult.

Ajax is key, but is difficult to write, too.

Declarative Ajax in the form of standard languages.

Links

formsPlayer, http://www.formsPlayer.com/
Sidewinder, http://www.formsPlayer.com/about-sidewinder
xH: The new programming language you already know, http://www.formsPlayer.com/xH
This talk, http://svn.x-port.net/svn/public/presentations/2007-05-10-mb-www2007/index.html