Cadastral Spatial Entity and Its Spatio-temporal Topology Relationship

There is strong spatial and temporal characteristic in cadastral information system.It has spatial characteristic by recording each parcel and buildings on it,and temporal characteristic by realizing the change of parcel and tracing the process of the change.Furthermore,because land is continuous and area is conservational,it must satisfy"mutually exclusive and complete coverage" topology relationship.So,how to model the cadastral entity and its spatio-temporal topology is most important in building a successful cadastral information system.Let us make a comprehensive view of those cadastral information systems that are being used.Some of these systems are static systems,which only record the present phenomenon of the parcel,but fail to record the process of parcel changing;some are temporal systems,which record the change of the parcel,but neglect to keep topology relationship of the parcel;others are spatio-temporal systems,which record the history of the parcel and part of its spatio-temporal topology,but neglect the necessity of"mutually exclusive and complete coverage" topology in cadastral information systems.This paper starts from static description of cadastral entity and its spatial topology,discusses the types of parcel change,develops the method of changing the cadastral topology by using cadastral changing event,and tries the way of separating all cadastral changes into two categories,namely,division and combination.The use of this method has four advantages.Firstly,it is suitable for recording spatio-temporal topology change when there is any alteration.Secondly,it combines the change of cadastral entity with the event of cadastral change and realizes the concept of spatio-temporal modeling based on event.Thirdly,it can realize the UNDO process by recording the changing event.Lastly,it can achieve record-locked when there is any sharing operation.