1. A system for supporting management of a collaborative activity by persons involved therein, the persons not being specialists in information technology, the system being implemented using a processor and a storage device accessible to the processor, and the system comprising: a representation of a model of the collaborative activity in the storage device, the model of the collaborative activity including model entities that are organized into hierarchies and provide access to information concerning the collaborative activity, the model entities having types including a goal model entity type, model entities of the type representing goals and/or projects of the collaborative activity and an initiative model entity type, model entities of the type serving to relate goal model entities across the model, and the hierarchies including a goal hierarchy whose members include at least one goal model entity, a given goal model entity belonging to only a single goal hierarchy and an initiative hierarchy whose members include at least one initiative model entity, each initiative model entity being capable of having as children one or more initiative model, entities and/or one or more goal model entities from one or more of the goal hierarchies; and a graphical user interface for the system, the graphical user interface being provided by the processor to a person of the persons, the processor providing outputs via the graphical user interface to the person and responding to inputs via the graphical user interface from the person by performing operations on a model entity including creating, modifying, and/or deleting the model entity, assigning the model entity to a parent in a hierarchy, accessing and/or modifying the information concerning the collaborative activity via the model entity, and displaying the model entity in a hierarchy of the hierarchies to which the model entity belongs.