Figure Proj.02 - detailed structure

Notice that the model the following figure shows the composite pattern and associations individually, rather than at the ProjectElement level. This has been done to help the understanding of the business rules.  In the design model it may be worthwhile moving these associations to ProjectElement and implementing the business rules using a rules or policy engine.<br/>ProjectElements can be related to each other, for instance an Activity can have predecessor and successor Activities. This will be explored in more detail in the next section.<br/>ProjectElements of the same type can be arranged into trees. This is shown using the Composite pattern [GoF], with the restriction [DAG] denoting that the composite forms a directed acyclic graph (no loops allowed) or [Tree] denotes that it is a strict hierarchy (an element can have only one parent at a given point in time). Note that the WBS Element hierarchy is restricted to the same Project and the Activity hierarchy is restricted to the same Project/WBS Element.<br/>