Abstract. In spite of the more advanced modularisation mechanisms, aspect-oriented programs still suffer from evolution problems. Due to the fragile pointcut problem, seemingly safe modifications to the base code of an aspect-oriented program can have an unexpected impact on the semantics of the pointcuts defined in that program. This can lead to broken aspect functionality due to accidental join point misses and unintended join point captures. We tackle this problem by declaring pointcuts in terms of a conceptual model of the base program, rather than defining them directly in terms of how the base program is structured. As such, we achieve an effective decoupling of the pointcuts from the base program's structure. In addition, the conceptual model provides a means to verify where and why potential fragile pointcut conflicts occur, by imposing structural and semantic constraints on the conceptual model, that can be verified when the base program evolves. To validate our approach we implemented a model-based pointcut mechanism, which we used to define some aspects on SmallWiki, a medium-sized application, and subsequently detected and resolved occurrences of the fragile pointcut problem when this application evolved.

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Program queries can answer important software engineering questions that range from "which expressions are cast to this type?" over "does my program attempt to read from a closed file?" to "does my code follow the prescribed design?". In this paper, we present a comprehensive tool suite for querying Java programs. It consists of the logic program query language SOUL, the CAVA library of predicates for quantifying over an Eclipse workspace and the Eclipse plugin BARISTA for launching queries and inspecting their results. BARISTA allows other Eclipse plugins to peruse program query results which is facilitated by the symbiosis of SOUL with Java -setting SOUL apart from other program query languages. This symbiosis enables the CAVA library to forego the predominant transcription to logic facts of the queried program. Instead, the library queries the actual AST nodes used by Eclipse itself, making it trivial for any Eclipse plugin to find the AST nodes that correspond to a query result. Moreover, such plugins do not have to worry about having queried stale program information. We illustrate the extensibility of our suite by implementing a tool for co-evolving source code and annotations using program queries.

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