Multiple Concerns in Aspect-Oriented Language Design: A Language Engineering Approach to Balancing Benefits, with Examples
Some in the aspect-oriented community view a programming language as aspect-oriented only if it allows programmers to perfectly eliminate scattering and tangling. That is, languages that do not allow programmers to have maximal quantification and perfect obliviousness are not viewed as aspect-oriented. On the other hand, some detractors of aspect-oriented software development view maximal quantification and perfect obliviousness as causing problems, such as difficulties in reasoning or maintenance. Both views ignore good language design and engineering practice, which suggests trying to simultaneously optimize for several goals. That is, designers of aspect-oriented languages that are intended for wide use should be prepared to compromise quantification and obliviousness to some (small) extent, if doing so helps programmers solve other problems. Indeed, balancing competing requirements is an essential part of engineering. Simultaneously optimizing for several language design goals becomes possible when one views these goals, such as minimizing scattering and tangling, not as all-or-nothing predicates, but as measures on a continuous scale. Since most language design goals will only be partially met, it seems best to call them ``concerns.''