Ontological foundations for state and identity within the object-oriented paradigm

Objects can be seen, at an abstract level, as information tokens made of two parts: an identification part and state, or value part. The identification part contains an object identifier different from that of any other object. The state part contains instead a structured value denoting the collective value of the attributes of the object. While the identifier assigned to an object remains fixed, the state is allowed to change, i.e. different values can be found in the state part of the object at different times. An object model with identifiers abstracts the formal properties of identity achieving a neat separation between object identification and object representation. Object identification becomes therefore a formal property preserved by the system. Traditional approaches in data and knowledge representation use instead some aspects of individuals´ state, which only occasionally satisfy the uniqueness and continuity properties of identity. The problem is that identificative attributes chosen at a given time, may carry different values or may not be unique as the context changes; in general, identification is conceptually different from representation. The paper proposes an ontological foundation for the concept of object state and identity, showing formally the equivalence with the infinite properties which are inherent in the cognition of real world distinct entities (Leibniz´ principle).