On the computational strength of pure ambient calculi

Cardelli and Gordon's calculus of Mobile Ambients has attracted widespread interest as a model of mobile computation. The standard calculus is quite rich, with a variety of operators, together with capabilities for entering, leaving and dissolving ambi- ents. The question arises of what is a minimal Turing-complete set of constructs. Previous work has established that Turing completeness can be achieved without using communication or restriction. We show that it can be achieved merely using movement capabilities (and not dissolution). We also show that certain smaller sets of constructs are either terminating or have decidable termination

Modelling dynamic web data

We introduce Xd¼, a peer-to-peer model for reasoning about the dynamic behaviour of web data. It is based on an idealised model of semistructured data, and an extension of the ¼-calculus with process mobility and with operations for interacting with data. Our model can be used to reason about behaviour found in, for example, dynamic web page programming, applet interaction, and service orchestration. We study behavioural equivalences for Xd¼, motivated by examples

Isolating JavaScript with Filters, Rewriting, and Wrappers

Abstract. We study methods that allow web sites to safely combine JavaScript from untrusted sources. If implemented properly, filters can prevent dangerous code from loading into the execution environment, while rewriting allows greater expressiveness by inserting run-time checks. Wrapping properties of the execution environment can prevent misuse without requiring changes to imported JavaScript. Using a formal semantics for the ECMA 262-3 standard language, we prove security properties of a subset of JavaScript, comparable in expressiveness to Facebook FBJS, obtained by combining three isolation mechanisms. The isolation guarantees of the three mechanisms are interdependent, with rewriting and wrapper functions relying on the absence of JavaScript constructs eliminated by language filters.