Using conventional and nested relational database systems for modelling CIM data

In the past, database management systems (DBMS) were predominantly used for business applications. A more recent application domain for DBMS comprises the so-called 'nonstandard' applications. The paper considers CAD/CAM applications and provides a brief overview of computer integrated manufacturing with particular emphasis placed on data modelling requirements. The basic object classes of a particular CIM application, the model of a manufacturing cell, are described. A conceptual model of a manufacturing cell is developed in the form of an Entity-Relationship schema. This semantic database schema is transformed into two different data models: the (pure) relational model and the nested relational model NF². The NF² data model allows nested relations in the form that attributes can be of type 'relation'. Thereby the hierarchical structure of an application can be preserved in the NF² schema, whereas the flat relational schema cannot preserve this structure within the database. Example applications from the field of robot motion planning were implemented, based on the data stored in these databases, in order to evaluate the design.