SISCweb is a framework to facilitate writing stateful Scheme web
applications in J2EE environments.

In addition to the source code, a small collection of simple examples
is provided as a war file "siscweb-examples.war" which can be deployed
in any recent J2EE server (e.g. tomcat 5.x) running under Java 1.4.

FEATURES

SISCweb features an interactive, REPL-based web application
development style. Developers can write applications interactively,
without ever bouncing the server, and, insofar as it is desirable,
without ever losing application state. (In fact, save for the Java
portion, SISCweb itself is written interactively in a REPL.)

Through the use of continuations, SISCweb does away with the
page-centric execution model typical of web applications. [*] Every
time a response is sent to the browser, the program execution flow is
suspended, to be then resumed from that exact point when the browser
submits a request. Some consequences of this approach are:

  - Programs are more easily structured around their problem domain
    rather than their presentation.
  - Developers are freed from having to manually manage the lifecycle
    of objects in the session. In fact, there is hardly any need to
    store objects in the session; when the browser submits a request
    and the program's execution flow is resumed, all the language-level
    variables the were in scope are again available.
  - Thanks to SISC's serializable continuations, accumulated program
    state is transparent to server restarts and (theoretically) to
    clustering.
  - Programs can be made resilient to page reloads and cloning with
    much less effort.
  - An extra security layer is added because URLs (which now encode a
    reference to program state) cannot quite be manipulated, hidden
    form variables are not needed anymore, and in general the automatic
    state management in SISCweb should be more difficult to fool than
    the ad-hoc solutions developers are forced to implement in
    traditional web applications.

SISCweb uses SXML to generate the content of the response, but any
other mechanism can be easily plugged on top of a basic set of the
response functions.

Additionally, features planned for future releases are:

  - A concise set of functionalities to build content (HTML, JPG, PNG,
    etc.)
  - SXML markup wizardries such as (img (@ (src ,get-image))) and more.
  - A robust continuation management engine: by v1.0 an application
    written in SISCweb should be as resilient to load as a traditional
    Java web application.

[*] More information can be found in this paper: Christian
Queinnec. "Inverting back the inversion of control or, continuations
versus page-centric programming". Technical Report 7, LIP6. May
2001. (http://www-spi.lip6.fr/~queinnec/Papers/www.ps.gz)

REQUIREMENTS

SISCweb requires a relatively recent J2EE application server (Tomcat
5.0 for instance) and Java 1.4.2. More detailed information is
contained in the INSTALL file.

STATUS

While currently about as featureful as PLT's web-server collection,
this release is strictly oriented to people already familiar with
Scheme and the continuation-based development approach. A concise
reference to the main modules is provided in the doc/ folder, and a
few basic examples can be found in the examples/ folder.

This release features a very simple continuation manager that removes
accumulated continuations based on an assigned time-to-live. More is
in store.

CREDITS

SISCweb is based on SISC (sisc.sf.net), a Scheme interpreter for the
JVM, and is heavily influenced by other Lisp web frameworks:

  - the PLT web server collection
    (http://download.plt-scheme.org/scheme/docs/html/web-server/)
  - SUnet (http://www.scsh.net/resources/sunet.html)
  - AllegroServe (http://allegroserve.sourceforge.net/)

A couple of initial design decisions were also lifted from Matthias
Radestock's servlet code in the contrib section of the SISC CVS tree.

CONTRIBUTING, BUG REPORTS

Comments, ideas, and bug reports are welcome at:

    acolo...@users.sourceforge.net

http://minstrel.dtdns.net/siscweb-examples/