Relationship of relationships and other inter-relationship links in E-R model

摘要

The concept of relationship has hitherto been defined as an association between entities. This definition is too restrictive and is inadequate for the modelling of certain phenomena occuring within the corporate context. When links appeared between relationships, the conventional Entity-Relationship model would transform the original relationships into entities and then establish a relationship between them. This transformation of the nature of a conceptual object does not stem from any need to represent a managerial reality, but from a modelling constraint. This article extends the notion of relationship by allowing for the expression of relationship between relationships whenever given conditions of the collections are verified. If these conditions are not verified, but links do exist between of given relationships, we suggest that these constraints be expressed using operators, such as exclusion, inclusion, simultaneity, totality, etc. These extensions all strive to achieve the same aim, which is to allow for clear modelling of the complex objects and links that occur within companies.