11 Apr 2007: SISCweb v0.5 Released

This release adds a space-safe implementation of Web Cells, consolidates the interface from Scheme to JSP/Servlets, and provides some incremental features and fixes.

Features

• An implementation of web cells, as as described in the paper Interaction-Safe State for the Web. New examples now help compare web cells, SRFI-39 parameters, state-passing-style and session attributes with respect to scope, backtracking and cloning.
• Much improved interface from SISCweb to JSPs and other standard J2EE components:
  • Bindings can now be explicitely single-valued or multi-valued, as in:
    `((a . 1) (b 2 3)).
  • The send-forward/* functions pass bindings to the dispatcher as request attributes for easy access via the JSTL and the like. Multi-valued bindings are passed as collection objects.
  • Vice-versa, attributes in a request forwarded to a Scheme program are now included in the bindings structure returned by get-bindings.
  • The SISCHttpServletRequest.getBinding*() methods are deprecated, and will disappear in the next release.
• Added publish/regexp to publish procedures using regular expressions. Sub-expressions can be optionally mapped to procedure parameters.
• The SISC libraries (sisc.jar, etc.) can now be shared across servlet contexts.
• Miscellanea:
  • better compliance of plain HTML output via send-html/*;
  • added siscweb/text module for generating plain text;
  • added sql/mssql module from LShift's Icing [*];
  • logging rotation;
  • further internal refactoring and compatibility fixes.

Fixes/Bugs

After a context restart, continuation tables persisted within sessions were not being purged of expired continuations. This was partially fixed in v0.4 by limiting the number of continuations per user, but is now completely resolved.

Looking Ahead

Objectives for the next SISCweb releases are:

• Faster SXML generation, precompiled if possible.
• Further work on including features from the Icing framework.
• Performance improvements, possibly including clustering.

Thanks

Special thanks for this release go to Ben Simon and Dan Muresan for their bug reports and contributions.

02 Sep 2006: SISCweb v0.4 Released

This release introduces improvements in continuation management, better performance under load, and logging.

Notes

• This release requires at least SISC 1.15, but SISC 1.16 is recommended because of radical improvements in I/O performance. This is also the first SISCweb release to work with SISC 1.16.

Features

• The configuration entries required in the web.xml file are now fewer, and are documented in the manual. Only one Listener and the adapter servlet are mandatory. Most configuration parameters are now optional and represented as environment entries.
• Values of environment entries, normally accessible through the application server's administrative interface, are picked up within a minute (provided that the application server allows changing them without a context restart.)
• Configurable resource-bounding limits the number of continuation groups per user, how frequently continuations can be created, how often expired continuations are removed, and how many are persisted. This makes SISCweb more resilient to load.
• SISCweb applications now respond to DELETE and PUT in addition to the usual GET and POST. (Continuations and REST can actually work well together, as explained by Anton Van Straaten.)
• Continuation storage via Hibernate is no more. Storing individual continuations was overall more expensive than serializing the whole continuation table, and altered the semantics of programs. Since application servers offer a variety of session storage mechanisms, including database persistence, the Hibernate option had no reason to be.
• The file WEB-INF/sisc.properties is picked up and used to initialize the SISC interpreter.
• SISCweb now logs most of its operations at various logging levels.
• Miscellaneous internal refactorings.

Fixes/Bugs

• After a context restart, continuation tables persisted within sessions were not being purged of expired continuations.
• Unfortunately this is still an open issue for some application servers, e.g. Tomcat (but not others, e.g. Resin.) Since the number of continuation groups per user is limited anyway, this is not a showstopper.

Looking Ahead

Objectives for the next SISCweb releases are:

• Faster SXML generation, precompiled if possible.
• Inclusion of some features from the Icing framework.
• Improvements in the interface between SISCweb and JSPs.
• Performance improvements, possibly including clustering.

Thanks

Special thanks for this release go to Ben Simon and Dan Muresan.