Research On Geographic Entity Based Spatio-Temporal Data Model And Query Processing

We interpret the geographic world as a combination of geographic entities(such as city,road,river).However,in GIS nowadays,these conceptually integrated entities are descried by points,lines and polygons,leading to division or multiple descriptions of entities.Using these geographic entities directly as the basic granularity for description,storage and manipulation can provide a bridge between conceptual understanding and practical application.The first issue arises of how to give a precise definition of geographic entities and what rules should be followed to classify and code them.The next difficulty is when there is a need for designing a data model that is generic enough for the geographic entities,able to reflect dynamic changes in geographic entities and relationships with other geographic entities.Based on the specifically designed spatiotemporal data model,the third question is how to generate and transform the existing geographic data into real geographic entity files? After getting enough geographic entity,they can be organized into entity libraries.The final question is how to use these entity libraries to solve practical issues.This paper firstly gives a clear definition towards geographic entities and illustrates the rules of classification and coding for complex geographic entities,extending the traditional methods.This paper gives a feasible solution to the second question by presenting a Spatio-Temporal Data Model of Geographic Entities(STDMGE),including conceptual model,logical model and physical model.which describes each geographic entity as geometry part,properties part and relations part,all of which are designed to combine and organize the multi-source data(traditional geospatial data,sensor data,relationship data among geographic entities,etc.).Also,the data model can reflect the dynamic changes of the geographic entity and realize the linkage update of the associated entities.Thirdly,this paper analyzes the main features of existing geographic data,and transforms the existing data into a physical entity file with a fixed format by processing the steps of parsing and recombining.Specifically,river entity and community entity are chosen to be transformed by the transforming algorithms.Finally,the paper integrates the generated river entity file and community entity file into the river entity library and the community entity library.By analyzing the application scenarios of the geographic entity library,the prototype system of the web version of the two entity libraries is designed.