Modeling web applications infrastructure with ASMs

• We provide ASM models of a script-capable web browser and a modules-based web server.
• Particular care is devoted to those aspects that allow executing modern web applications.
• These models have explanatory value in themselves, and could be used for a more formal validation.
• In addition, we show how a continuation-passing semantics can be used to good effect in ASM models.

We describe via Abstract State Machines the major ingredients of contemporary web applications: a web browser running JavaScript programs and a web server dispatching requests to one of several modules, each one representing a class of established web application frameworks.The web browser model comes in four levels, namely transport, stream, context and browser level, and is focussed on the interaction with possibly multiple servers (which requires a concurrent computation model) and on script execution (which requires a dynamic assignment of agents to programs). The server model is focussed on the Request–Reply pattern, and specifies a delegation strategy where the handling of a request is entrusted to a module. We show how several major frameworks for web applications can be described as progressive refinements of a number of basic modules. Three modules are further detailed: static file transfer, CGI and generic scripting modules.