[ANN] Altitude

Hi all,

One of my side projects for the last few years has been to experiment
with new ways of writing web applications, learning from our
experience with Seaside, but moving beyond it and trying to keep pace
with the state of the art in web application design. This hasn't been
a big secret—I've talked about the project and given demos in various
places—but I've been holding off on open-sourcing it until I had
something that I felt was ready for public scrutiny. Well, recently
Chris Cunnington would have none of that and challenged me to release
it already or shut up about it. So, here it is. ;-)

The framework is called Altitude, and released under the MIT license.
It's a brand-new, from-scratch HTTP server and application framework
written on top of Xtreams. It's still pretty raw. There's lots of
features missing and some functionality is present but completely
untested, as I've implemented things as I need them for my
application. There's no documentation and very few comments.

If you want to play around with it, execute the attached load script
in an up-to-date 4.4 image. The project repository is here:

    http://source.wiresong.ca/al



Colin

On Tue, Jul 17, 2012 at 3:30 PM, radoslav hodnicak <[hidden email]> wrote:
> Can you describe how it compares (or doesn't) to Seaside or other web
> technologies?

Sure. Seaside is probably the best comparison. I cut my Smalltalk
teeth writing a Seaside app, so it's had a huge influence on Altitude.

Altitude will feel familiar to those who've used Seaside before. It
has Component trees that render themselves using a canvas-style
protocol, and uses blocks as callbacks. Like Seaside, Altitude takes
care of generating urls and form-field names, so application
developers don't have to write a lot of code to route requests or
marshal server state into strings.

The main difference between Altitude and Seaside is that Seaside is
session-oriented, Altitude is resource-oriented. Seaside generates
unique urls for every interaction with the user, while Altitude
generates RESTful urls. The upside of that is that Altitude is more
cacheable than Seaside and has (potentially) more scalable memory
usage than Seaside. The downside is that it lacks Seaside's inherent
security. (Implementation note: Altitude doesn't use continuations. An
early prototype did have an implementation of call/answer based on
partial continuations, mostly to prove it would work, but I haven't
needed that in practice, so I took it out.)

Another difference comes from Xtreams. Seaside implements several
server-adaptors that allow it to work with various HTTP
implementations, like Kom, Zinc, Swazoo etc. Altitude implements its
own web server on top of Xtreams and takes full advantage of the
flexibility that Xtreams offers. Altiude uses Xtreams pervasively and
it's a huge improvement over the classical ST-80 stream protocol, both
in terms of design flexibility and performance.

Finally, Altitude provides less insulation form HTTP than Seaside
does. Seaside was designed to handle the details of HTTP so that the
developer can focus on his application. Modern web applications,
however, make more use of the features and details of HTTP (via AJAX,
for example), than in the past, and so Altitude exposes HTTP to the
application more than Seaside does. This may be because of Altitude's
relative immaturity; we'll see how it develops.

It would probably be good to implement some example applications in
Altitude, so people can see how the compare to the Seaside versions.

Colin