see Project Management
What Is A Pro Ject? An arbitrary collection of activities? It's definitely a Model (or the result of a Model).
It may be a simplification process of taking a messy Human System and pre-defining a vector of clear action with intended specific outcomes.
It may be a way of meta-defining a problem in a way that avoid the asking of uncomfortable questions. "Why do we keep doing this?"
David Allen [gives](http://david.davidco.com/David Co/davidallen.nsf/dx/goodkeytodefiningprojects) one definition.
Laurent Bossavit's thoughts
Sometimes it's about the boundary of a Contract or Commitment.