Abstract
Electronic mail (email) systems have grown in complexity to the point where their reliability and usability are coming into question. The authors of individual email components are widely distributed in both time and space, bound together only by message structure and transfer protocol specifications; consequently filters, autoresponders, and various security features may interact in unanticipated and, often, incomprehensible ways. This paper describes a formalism for modeling and composing specifications of email features, and a feature interaction detection methodology based in part on human intuition and in part on simulation and formal test coverage. The appendix lists 27 interactions found from applying the methodology to ten common email features, a result of independent interest considering the age and relative maturity of the email domain. The paper then proceeds to categorize the interactions according to their impact on the design of the system. This includes a design study of the most natural ways to fix the undesirable behaviors. From this we can infer non-modular dependencies among the features, leading to the result that 9 of the 10 features must be revised (and a custom user interface must be built for them) after they are composed and after feature interactions are detected. This pervasive nonmodularity shows that feature interaction analysis is necessary to optimizing the correctness of an email system design.
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Hall, R.J. Fundamental Nonmodularity in Electronic Mail. Automated Software Engineering 12, 41–79 (2005). https://doi.org/10.1023/B:AUSE.0000049208.84702.84
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DOI: https://doi.org/10.1023/B:AUSE.0000049208.84702.84