1. Concepts from the object-oriented approach describes the structural or static aspects of systems.
    2. High-level Petri nets net ( called the object control structure (ObCS) of the object ) describes the dynamic or behavioural aspects.
    3. A petri net is a directed bipartite graph whose nodes are either places (shown as circles) or transitions (shown as rectangles) which are connected by arcs. Each places contain any number of tokens which may carry values ( conventional values or references to other objects ). A transition may feature a precondition that is a Boolean expression which may involve the variable labelling the input arcs of the transition.
    4. An object is an entity featuring 4 components -- Services, behaviours, states, presentation