Representing Structure in a Software System Design ◾ 19
© 2010 Taylor & Francis Group, LLC
intersection? e focus on individual intersections now became a serious disadvantage: the
rules were clearly going to become very complicated. It took a little time before the teams
realized that they must consider the question in the larger span of a whole road or even the
whole layout.
On applying the notion of span to describe the behavior of an individual car as it
encounters successive intersections, it becomes immediately clear that the appropriate
span is the car’s complete purposeful journey across the bounded layout. Nothing else can
adequately represent the behavior of real cars and drivers. (Of course, in the real world
there are exceptions ...