Heterogeneous goods in transportation systems

Doktorsavhandling, 2007

This thesis presents research regarding the impact differences in goods type have on the control of a transportation process. It also explores how the object-oriented family of methods are used and can be used in analysing and designing transportation systems. The aim of the research is to develop knowledge on how to control a transportation system, capable of accommodating the requirements of heterogeneous goods and to identify key factors for the design of such a system by using object-oriented methods. The theoretical framework that is used is based upon three approaches. The first approach is that of heterogeneous goods, of how differences in goods type may cause cost increases in transportation systems. The second approach is that of systems theory in general and of cybernetics in particular. The third approach is that of object-orientation. Object-oriented methods are prominent in computer programming mainly because of their aptness to efficiently partition even the most complex of computer programs into manageable, interactive, and scalable code repositories – objects. The main task when controlling a transportation system is to handle complexity. Transportation systems are inherently complex, and this complexity is divided into three types: descriptive, computational, and uncertainty-based. The control of a transportation system is divided into three control scopes, each corresponding strongly to one of the three complexity types. In this thesis, it is found that heterogeneous goods increase complexity in transportation systems, and that this complexity mainly manifests itself as uncertainty-based. When designing a transportation system, it has been shown that object-orientation can be used to reduce complexity and to embed mechanisms that contribute to further complexity reduction. Eight case studies were performed and the cases were modelled and analysed using object-orientation. This resulted in a class library that is a synthesis of the object models of all the cases and consists of diagrams that evolved during the modelling process, as is consistent with the object-oriented techniques. It is concluded that object-orientation as a modelling method is well suited for analysis and design of transportation systems.