Reasearch on the Change-of-feature Based Spatio-temporal Object Relational Data Model

The spatio-temporal data is our cognition to external matter and the spatio-temporal data model is the fundamental basic to manage the spatio-temporal data. The spatio-temporal object is always changing so we need a spatio-temporal data model which can reflect the change information and change reason and roundly and exactly describe the spatio-temporal world. At the same time more and more demands to spatio-temporal data are proposed, but now the research of the spatio-temporal data model still is on the stage of theory research and can not implement the real application. We proposed a new model-the change-of-feature based spatio-temporal object relational data model by researching and analyzing the current spatio-temporal data models. This model reflects the changes of object and changing reason. Because it used the object relational way to implement it is easy to combine with current mainstream databaserelational database. The article mainly developed the feature change and introduced the concept model and its implement and finally gave an example of implementing our model in the agriculture management. The article is an attempt to resolve the implementation of the spatio-temporal data model. ∗ Corresponding author. [email protected] 1. PREFACE The research about the spatio-temporal data model sprang up in 1970s and until now many scholars had designed and proposed many Spatio-Temporal models. At the same time more and more demands to spatio-temporal data were proposed. But until now there is no really commercial spatio-temporal database software and current spatio-temporal data model cannot well effectively integrate with the mainstream relational database technology. Now the instances of really exporting the spatio-temporal database to GIS are few. The reason causing this problem included: (1) the matter of the spatio-temporal data model. The most of spatio-temporal data model having proposed emphasized particularly on theory research and divorced from the real application; (2) the matter of the spatio-temporal database implement technology. The spatio-temporal data include four dimensions information but the storing way of mainstream relational database is two dimensions relational table, so it is very difficult for relational database to directly manage spatio-temporal data. Now the spatio-temporal data models (Cao, 2001; Langran,1992; Peuquet et al, 1995; Cui et al,2004,; Jang et al , 2005; Zhai et al ,2005) generally included the following: Snapshots (Ross 1985), Spatial Temporal Cube(Hagerstand 1970; Rudcer 1977; Szego 1987), Base State with amendments( Langran 1990; Peuquest, 1994), Space-time Composite (Chrisman, 1983), Spatial Temporal Domain (Peuquest,1994),Event Based Spatio-temporal Data Model (Peuquet D.J ,1995),feature-based spatial-temporal data model ( W.H.Cui and W.Z.Shi,1995)and ect. These models had respective advantage and disadvantage and among them the feature-based spatial-temporal data model was a modeling way on higher abstract level and was built on good cognitive view on geographic information. At the same time it defined and built spatial relation and aspatial relation by using object-oriented principle and method. But this model can not carry out in depth study on change process and change reason of the spatio-temporal object so it cannot implement application. The article expands the feature-based spatial-temporal data model and then proposes the change of feature based spatio-temporal object relational model, which emphasizes the concept of event and state and implements the model by object relational way. The article attempts to promote the research and the extensive application of spatio-temporal data model. The rest of this article is structured as follows. In Section 2 we introduced the conceptual model, implementing way and advantage of the change of feature based spatio-temporal object relational model. Section 3 described how implement the model and gives an example of application. Finally Section 4 gives some conclusions. 2. THE CHANGE OF FEATURE BASED SPATIO-TEMPORAL OBJECT RELATIONAL MODEL 2.1 Outline of the feature based GIS How to organize data is an important issue in GIS system construction. The problems in GIS are to large extent aroused by the design of data model and the expression way of data (Peuquet, 1984; Tang et al, 1996). In the development process of GIS with the increasing development of the cognitive manner and cognitive means to the objective world there are two ways to organize data: layer based organization of data and feature based organization of data. The human’s cognition to world is based on the geographic feature so the feature based organization of data can effectively describe the geographic object or phenomena and is easy to implement, at the same time it can be more easily understood and accepted by users