Multiple Concerns in Aspect-Oriented Language Design:
 A Language Engineering Approach to Balancing Benefits, with Examples
				  by
		  Gary T. Leavens and Curtis Clifton

			       Abstract

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.''

Keywords: aspect-oriented programming language design, concerns, goals,
quantification, obliviousness, scattering, tangling, 
ease of reasoning, ease of maintenance, compromise, tradeoff, balance.

2007 CR Categories:
D.1.m [Programming Techniques]
        Miscellaneous --- aspect-oriented programming;
D.2.10 [Software Engineering]
        Design -- methodologies;
D.3.0 [Programming Languages]
	General --- aspect-oriented language design;
D.3.3 [Programming Languages]
	Language Constructs and Features --- control structures,
        modules, packages, procedures, functions and subroutines, advice,
        aspects, quantification, obliviousness.

To appear in \emph{SPLAT '07}, March 12, 2007, Vancouver, British
Columbia, Canada. 

Copyright (c) 2007 ACM ISBN 1-59593-656-1/07/03...$5.00

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