TABLE OF CONTENTS There are three established data models used in databases today:
the hierarchical model;
the network model;
the relational model.
Research has suggested the use of object-oriented programming to provide efficient data models for manufacturing automation. Object-oriented databases are now available commercially, although at present their use is restricted to research laboratories.
Historically, the hierarchical model and the network model were developed around the same time, during the 1960s, while the relational model was not proposed until several years later. Both the network and hierarchical models are tightly linked to the application chosen, while the relational model is more flexible, and not constrained in this way.
The structure described above provides a means of storing data that is of use to the company but no attempt is made to look at the relationships between the individual elements of the data. Typically, the company may be keeping records of the assembly of a finished product that contain data relating to cost, number in stock, the part elements that go to make up the assembly, the engineering drawing codes and other manufacturing information. This information can be considered to be in the form of subsets, such as the list of parts used in an assembly being a subset within the total amount of data on the assembly. This tree-like form of representing data leads to the implementation of hierarchical structures that are difficult to operate using paper-based methods but can be run using computers.
The hierarchical...
