allowing/support creation of un-foreseen uses/activities by unknown people
http://en.wikipedia.org/wiki/Generative_systems Generative systems are systems that use a few basic rules (Game Rule) to yield Pattern-s. Depending on the rules, the patterns can be extremely varied and unpredictable. One of the more well-known examples is Conway's Game Of Life, a Cellular Automata. Another example is Boids. More examples can be found in Generative Music, Generative Art, and, more recently, in Video Game-s such as Spore.
do Declarative systems make this easier?
definitely Loosely Coupled helps