Many interesting questions about the software quality of a code base can only be answered adequately if fine-grained information about the evolution of quality metrics over time and the contributions of individual developers is known. We present an approach for tracking static analysis violations (which are often indicative of defects) over the revision history of a program, and for precisely attributing the introduction and elimination of these violations to individual developers. As one application, we demonstrate how this information can be used to compute ``fingerprints'' of developers that reflect which kinds of violations they tend to introduce or to fix. We have performed an experimental study on several large open-source projects written in different languages, providing evidence that these fingerprints are well-defined and capture characteristic information about the coding habits of individual developers.

A trace monitor observes an execution trace at runtime; when it recognises a specified sequence of events, the monitor runs extra code. In the aspect-oriented programming community, the idea originatedas a generalisation of the advice-trigger mechanism: instead of matchingon single events (joinpoints), one matches on a sequence of events. The runtime verification community has been investigating similar mechanisms for a number of years, specifying the event patterns in terms of temporal logic, and applying the monitors to hardware and software.

In aspect-oriented programming, one can intercept events by writing patterns called pointcuts. The pointcut language of the most popular aspect-oriented programming language, AspectJ, allows the expression of highly complex properties of the static program structure.We present the first rigorous semantics of the AspectJ pointcut language, by translating static patterns into safe ( i.e. range-restricted and stratified) Datalog queries. Safe Datalog is a logic language like Prolog, but it does not have data structures; consequently it has a straightforward least fixpoint semantics and all queries terminate.The translation from pointcuts to safe Datalog consists of a set of simple conditional rewrite rules, implemented using the Stratego system. The resulting queries are themselves executable with the CodeQuest system. We present experiments indicating that direct execution of our semantics is not prohibitively expensive.

An aspect observes the execution of a base program; when certain actions occur, the aspect runs some extra code of its own. In the AspectJ language, the observations that an aspect can make are confined to the current action: it is not possible to directly observe the history of a computation.Recently, there have been several interesting proposals for new history-based language features, most notably by Douence et al. and by Walker and Viggers. In this paper, we present a new history-based language feature called tracematches that enables the programmer to trigger the execution of extra code by specifying a regular pattern of events in a computation trace. We have fully designed and implemented tracematches as a seamless extension of AspectJ.A key innovation in our tracematch approach is the introduction of free variables in the matching patterns. This enhancement enables a whole new class of applications in which events can be matched not only by the event kind, but also by the values associated with the free variables. We provide several examples of applications enabled by this feature.After introducing and motivating the idea of tracematches via examples, we present a detailed semantics of our language design, and we derive an implementation from that semantics. The implementation has been realised as an extension of the abc compiler for AspectJ.