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Ajax have allowed JavaScript programmers to create interactive, collaborative, and user-centered Web applications, known as Web 2.0 Applications (W2As). W2As behave as distributed systems because processors are user machines that are used to send and retrieve messages between them. Unsurprisingly, these applications need to address the same causality issues present in distributed systems like nondeterministic behaviors for the same input and reasoning about distributed computations. JavaScript programmers overcome these issues using rudimentary and alternative methods that ignore fully the distributed computing theory. In addition, these methods need to modify intrusively W2As in order to work.

In this paper, we analysis how causality issues affect current W2As, and present WeCa, a non-intrusive mechanism to eliminate nonde terministic behaviors and to reason about distributed computations. WeCa is inspired by distributed computing and aspect-oriented pro- gramming ideas like vector clocks and stateful aspects. We illus- trate WeCa in action with several practical examples from the realm of W2As. For instance, we use WeCa to analyze the flow of infor- mation in W2As like Twitter.