Seaside, an acronym that stands for “Squeak Enterprise Aubergines Server with Integrated Development Environment,” is computer software, a web framework to develop web applications in the programming languageSmalltalk. It is distributed as free and open-source software under an MIT License. Seaside provides a component architecture in which web pages are built as trees of individual, stateful components, each encapsulating a small part of a page. Seaside uses continuations to model multiple independent flows between different components. Thus, it is a continuation-based web framework based on the ability to manipulate the execution stack of some implementations of Smalltalk.
Key features
Seaside's implementation of continuations was an initial point of interest in its first several years of existence following its 2002 release. Continuations provide a mechanism for rollback and resumption, a useful provision for the web browser environment in which refresh and back buttons may interrupt the flow of processing. This resolves many common issues with running web applications, like adequately sustaining the state on the server-side even when the web browser’s ‘back’ and ‘forward’ buttons are used. Continuation servers give the developer the ability to maintain state on the server in a scalable manner. The subsequent improvement of web browser implementations of JavaScript since 2002 has made the continuations aspect of Seaside less significant, by allowing client browsers to keep track of state better. A distinctive feature of Seaside is its integrated development environment, providing access to development tools and debugging support within an application. In development-mode, unhandled errors are reported to the web page; developers can access and alter the program code and state directly from the web page, allowing bug identifying and fixing processes to occur within an integrated development environment. A Seaside application is a set of interacting components. Each one stores state across page views and can render itself to the HTML stream. Thus, it is straightforward to write a component once and then reuse it elsewhere in an application. Seaside also supports the notion of tasks, which allow a programmer to describe the high-level logic of component interaction. Seaside is not template-oriented, and does not offer generating or using HTML templates; HTML markup is generated programmatically. Seaside uses callbacks on closures to specify actions to be taken when clicking on a link or submitting a form. The developers and users of Seaside argue that this helps enforce separation of structure from content and presentation. Seaside's combination of components, callbacks, and closures can significantly reduce the semantic gap between a complex workflow and its representation in code. Seaside supports Ajax through integration with script.aculo.us and jQuery. Seaside also supports Comet-style server-push technology. Seaside can work with either Smalltalk-based web server implementations or other non-Smalltalk ones.
Philosophy
Over the last few years, some best practices have come to be widely accepted in the web development field:
Share as little state as possible.
Use clean, carefully chosen, and meaningful URLs.
Use templates to separate the model from the presentation.
Seaside deliberately breaks all of these rules. Avi Bryant describes it as a 'heretical' framework. He argues that this careful and reasoned rejection of the conventional wisdoms of web development has led to a very effective model for developing web applications.
Ports
The main development of Seaside is implemented in Pharo Smalltalk. Ports for other Smalltalk dialects exist. The original development of Seaside was done on Squeak in the early 2000s. Michel Bany implemented ports to VisualWorks through Seaside version 2.7; Cincom Systems supports Seaside as part of VisualWorks as of early 2008. Instantiations announced Seaside support in its VAST Platform version 8.0 in 2009. The VAST Platform has continued to support Seaside through its latest version. Esteban Maringolo maintained the 2.8 port, plus some other add-ons for Dolphin Smalltalk X6. Gemstone Systems implemented a port to Gemstone/S. A port of 2.8 was completed for GemStone, and a preliminary version of 3.0 runs on GNU Smalltalk 3.0a and later.
Criticisms
Compared to other web frameworks, Seaside is memory intensive. One session could accumulate several hundred kilobytes of RAM. A later release, version 2.8, significantly reduces this size.
