Design And Implementation Of Location Information System Supporting Compound Query

Geographic(location)information system can analyze and process the spatial topology information and attribute information of geographic entities,and then feedback the parsed results to users.Existing location information systems for ordinary users generally lack the ability to query by using multiple complex conditions.Specifically,the existing systems usually use a single data source as the basis of spatial query,and the data richness is not enough to support compound query.In addition,the complex spatio-temporal characteristics,multidimensionality and mass data characteristics of spatial data greatly increase the difficulty of system development.In order to reduce the complexity of the system,the current location information systems that support compound query are basically customized for the specific field.More importantly,compound queries involve a lot of complex spatial calculations.Although the existing spatial index technology can reduce the number of calculations for a single query,when the compound conditions and the amount of spatial data increase,the spatial index cannot be optimized from a global perspective.Therefore,this paper mainly researches and implements a more general and better-performing location information system that supports compound query.The main design and implementation of this paper are as follows:(1)First,define the compound query rule that can meet a wide range of needs.In this paper,the complex query is carried out by combining the geographic entity's attribute restriction and the spatial relationship between other geographic entities.For query performance considerations,first optimize the data index and use a variety of storage technologies.Then,reasonably divide compound conditions into multiple steps for query.Dynamically adjust the query strategy based on the results of the previous step to reduce the overall execution time of the query.In particular,the spatial relationship calculation stage will have three different calculation strategies based on previous results,which can minimize the total number of spatial calculations.Finally,performance tests were carried out for different stages of optimization work,and the performance of compound query was greatly improved,which verified the effectiveness of the design.(2)Realize the location information system through middleware and multiple software frameworks.The system covers componentized user interface,data ETL tasks and management,compound query,user and authority management and other map-related functions.Among them,the GeoThreadPool is designed and implemented for the crawling characteristics of geographic data.In the thread pool,a multi-level decomposition algorithm for geographic regions is implemented,which can efficiently divide the search range of geographic data.Moreover,the adaptive crawl frequency algorithm implemented in the thread pool can automatically adjust the number of threads and crawl frequency for data crawling according to the characteristics of the data source server.Finally,the system is tested in terms of function and performance,and the test results verify the effectiveness and reliability of the system and can meet the design requirements.