Study On Restful GIS Services Mashup And Software Development

GIS service is the inevitable result of the combination of Geographical Information System and Web service technology, which is widely used for the sharing of heterogeneous geospatial data and the interoperating of geoprocessing operations in distributed platform-independent and language-independent environments. Since function limited single GIS service cannot satisfy the demands of internet users anymore, it is necessary to dynamically mashup those existing GIS services to implement more complex tasks. However, the application of the research for GIS services mashup is still infancy with the following limitations:1) An efficient search method is not available to help user quickly find the required services within vast GIS service resources.2) Few researches have been done on the GIS geoprocessing services mashup according to the lightweight client requirement.RESTful (Representational State Transfer) GIS services provide a new opportunity for the agile mashup of GIS services in lightweight client. This research represents an effort to explore conceptual basis, algorithms and architecture of RESTful GIS services mashup.The main scientific findings of this research include:1) This research examines the technical backgrounds of RESTful GIS service and the current standards of metadata and geospatial metadata, and reveales that those standards are too complex for non-professional persons to operate and lack the standards for GIS geoprocessing service. Thus, new metadata for RESTful GIS data service and RESTful GIS geoprocessing service have been proposed respectively based on their different characteristics and current national standards.2) A flexible framework for users to draw up personalized GIS data service search mechanism has been designed. In GIS data service search, Matching Degree is introduced to measure the matching degree between GIS data service and user requirement. Method to calculate content matching degree has been proposed based on similarity theory; likewise, Algorithm to calculate bound matching degree has been developed based on topological theory. Also, Number of effective services is introduced to speed up the matching convergence and increase the matching efficiency. Match threshold is introduced to filter the search results.3) This research improves GIS geoprocessing services search algorithm. Two limitations of graph search algorithm in GIS geoprocessing services search have been analyzed:Arduous construction of dependence graph and unsolvable GIS geoprocessing services search with multiple inputs and multiple outputs. Accordingly, Breadth-first Reverse Share Pruning AND/OR Tree algorithm has been proposed in this research. This algorithm proposes a reverse AND/OR tree to simplify the search by converting mesh AND/OR graph to AND/OR tree. This research also has developed a rule for converting complex types of services into a combination of two simple types of services. Furthermore, shared tree has been introduced and search efficiency has been improved by deleting the AND sub-tree.4) With consideration of the difficulty in building distributed heterogeneous geospatial data which are stored in different ways into input parameters of GIS geoprocessing service, GIS geoprocessing service that copies the geospatial data is proposed to simplify the construction of FeatureSet parameter, thereby achieving the implementation of GIS geoprocessing services mashup based on script-level codes. The encoding time and difficulty in system development have been reduced also. Meanwhile, the geospatial data's security has been effectively safeguarded by avoiding publishing the server, database user name and password.5) Based on the RESTful GIS service, the architecture of RESTful GIS services mashup platform has been presented. The functions of system levels and their inner-relationship have been clarified. The architecture is further described in four aspects, (i.e.) Dataflow, User Role; Platform Function and Platform Interface. It provids holistic framework and top-level guidance for studying mashup technologies and implementing mashup platform. Under the guidance of the overall architecture, the GIS service description and registration, the search algorithms and the mashup template execution have been implemented, and the RESTful GIS service mashup platform has been built. 6) The role of RESTful GIS Service mashup platform is described from perspective of service provider and consumer. Some specific application cases have been designed to further verify the feasibility and applicability of the proposed system.