Study On Spatio-Temporal Data Model Based On Event Semantics

It has become an important research direction to develop spatio-temporal modeling technology, to get the whole description information about the space, time and attributes of the geographic phenomenon, to realize the storage, management and utilization of spatio-temporal data, to complete the analysis of time series, space and spaio-temporal relationship. Based on the broad investigation and deep analysis to the character of spatio-temporal data and fruit of former research, the author provides the concept model, logic model and physical model of spatio-temporal information modeling from the perspective of geographical cognition and event semantics, makes systemic study on the expression, the record and the utilization of spatio-temporal information and spatio-temporal relationship, the main fruits of the study are described as follows: The author makes discussion on practical meaning to develop spatio-temporal data model and the background of the utilization of spatio-temporal geographic information system, makes summarization on the status of former research and development about the spatio-temporal data model, and makes remark on the characters and the problems of various models, provides the main problem about spatio-temporal modeling at present.In order to describe of semantic cognition about spatio-temporal information, the author casts back the geographic cognition, makes retrospect on the research on geographic cognition of geographer, psychologist, philosopher, neurologist and linguist, introduces the cognition about what, where and when and the procedure of getting the spatio-temporal knowledge. Based on the above description, from the two perspectives of temporal view of philosophy andcognition science----time series and time scale, the author introduces the conceptof spatio-temporal semantics, brings forwards the idea of spatio-temporal modeling based on event semantics.The author analyzes space and time these two basic existence form of substance, studies space, time and attribute these three basic characters of geographic entity, provides the idea to divide time semantics into event semantics, to build spatio-temporal model based on event semantics. The author analyzesevery aspects relating with event, such as object status change, space location change, object attributes change and object change etc., provides saptio-temporal description way using five-domain, and gives detail description about each component of it.The author summarizes the two former ways to express spatio-temporal information, namely the way to express spatio-temporal information with time tag and the way to express with event and procedure, gets the pith of these two ways, provides the logical model based on event semantics, and defines the model, class and object with UML, makes time class, space class, event class, attribute class and relationship class using object-oriented technology. The author also gives preliminary study on changes accord with function relationship and the class about it is provided in the paper.The author expatiates on spatio-temporal topology relationship which satisfied with mutually exclusive and complete cover in space, defines the rules of spatio-temporal changes, expounds the mechanism of recording and dynamic building of these changes driven by event, the problems of restoring and analyzing spatio-temporal relationship are solved by the model.The author also expounds the storage of long-dated and short-dated spatio-temporal information. Combined with present storage way, the author provides improved way for short-dated information storage, namely the dynamic multi-index ground-amend way. The way is flexible, it makes a balance between speed and capacity, the key is the switch-point between speed and capacity. For long-dated information storage, based on the analysis of three-period policy provided by Professor Tang, the author provides part-frequency strategy according to change frequency. According to continuance of change, defines those related more with present as current age, those related less as middle age and those related lest as old age.The permission and security of history in the model are also analyzed in the paper, which provide ways to access and resume history according to permission, thus makes legal history data safe.Operations on these spatio-temporal data using five-domain component, such as union, minus, Descartes product* join and projection are also provided in the paper. The utilization of spatio-temporal information such as query, statistics andanalysis can be easily done using the combination of these basic operations.The cadastral information system is taken as example in the paper. Based on the expandable relation DBMS, the cadastral spatio-temporal model is build using the principle described above, time table, space table, event table, attribute table and relationship table are set up here, the program about query on time, location, attribute, event and trace about one parcel or entire area are provided. Finally a real example system—Wenzhou cadastral information system are provided in the paper, and the results of functions related with spatio-temporal data such as trace of range, reappearance of history, query, statistics and analyze about history are showed in the paper.The theory of spatio-temporal modeling is further enriched by the model provided in the paper, which makes a welcome step in spatio-temporal modeling, provides a new direction for further research on spato-temporal modeling. But spatio-temporal modeling is still a challenging project, is still in the stage of theory improvement and method practice, more study and practice are still needed to realize it.