Specifying a forest harvest scheduling system which includes wood properties.
This dissertation aims to specify a forest harvest scheduling system which includes wood properties in the harvesting decisions for the long-term (strategic) planning horizon. This system will be used by plantation forestry companies which supply wood to pulp manufacturers, who desire a more uniform raw material entering pulp mills so that a more uniform product results. Vertically integrated forestry companies would benefit particularly, as the allocation of timber to mills, as well as the timber transport costs, are included in the system. It has been found from literature that only one forest harvest scheduling system exists which includes wood properties in the harvesting decision; however, this system was a short-term (operational) system. To our knowledge, no other system which includes wood properties in the harvesting decision has been reported. As the forest harvest scheduling system is affected by the forest, transport, mill and forest planning domains, their procedures and constraints, these domains were described first, and the forest harvest scheduling system described next. The system and the environments (or domains) were specified with two techniques: semi-formal and formal methods. The semi-formal method used the Zachman framework to structure the specification. The Business owner’s view of the system was used. This framework uses complementary models such as entity-relationship diagrams, business process diagrams and state charts to describe aspects of the same thing. The formal method specification used the Z notation which is based on set theory and predicate logic. The semi-formal and formal specifications together form a complementary specification. The semi-formal specification is more understandable by clients, but could contain inconsistencies. The formal specification is more precise, but because it uses mathematical notation, is not as well understood. The semi-formal specification describes more features, while the formal specification describes the features in depth. The forest harvest scheduling system specified uses wood properties in the harvesting and timber allocation decisions over the strategic planning horizon. When the system is implemented, wood having more uniform properties will be delivered to the mill, ensuring a more uniform pulp product.