Part-Whole Relations in Object-Centered Systems: An Overview

Knowledge bases, data bases and object-oriented systems (collectively called Object-Centered systems) all rely on attributes as the main construct used to associate properties to objects; among these, a fundamental role is played by the so-called ‘part-whole’ relation. Such a structural information usually requires specialized inference and update mechanisms, but rarely do current modeling formalisms and methodologies give it a specific, ‘first-class’ dignity. The main thesis of this paper is that the part-whole relation cannot simply be considered as an ordinary attribute: its specific ontological mature requires to be understood and integrated within data modeling formalisms and methodologies. On the basis of such an ontological perspective, we survey the conceptual modeling issues involving part-whole relations, and the various modeling frameworks provided by knowledge representation and object-oriented formalisms