Research On GIS Services Chain Integrated Model And Realization Based On Workflow

Since the end of last century, the GIS Services has become a new mark of GIS (Geographic Information System) technology. The research on GIS Services has been turning from theory to application. With the major shift of GIS Services application from simple calling of single service to composition of multiple services, the research of GIS Services chain has been put on the agenda. Currently, GIS Services chain is mainly divided into two types. One is the composition of GIS and business flow application. The other one is the composing of complex GIS Service from single GIS service in flow mode. This dissertation puts more emphasis on the former one. Based on the analysis of the theory and technology, a new distributed and integrated model of GIS Services chain and visual modeling is put forth. Several key issues of GIS Services chain application are studied which include rapid indexing mechanism of distributed spatial data, efficient processing of massive Remote Sensing image data and distributed collaborative editing data model. Based on GIS Services and workflow, a prototype system called Urban Planning GIS (UPGIS) is designed and realized to study the development of GIS Services chain system with workflow technology.The main research contents are listed as follows:1. Based on the characteristics of GIS data and application, the author brings forth some terminology of GIS Services and GIS Services chain with reference specifications of international organization such as OGC (Open Geospatial consortium), ISO/TC211 and WfMC (workflow Management Coalition). For the first time, the author proposes terms such as micro-chain, pre-service/post-service, pre-condition/post-rule based on the meaning of "chain".2. From the viewpoint of application, the research puts forth GIS Services chain conceptual reference model by referencing reference model of workflow. Furthermore, author gives the five steps for realization of GIS Services chain: abstracting the business and service, definiting GIS Services chain, discovering and evaluating GIS Services, GIS Services chain visual modeling and executing and monitoring of GIS Services chain. Then, a hierarchical deploy model with five tiers is discussed in research: presentation layer, Web application layer, integration layer, services layer and data layer.3. With the analysis of distributed GIS application and technologies, the author brings forth a kind of distributed GIS integrated model based on workflow and GIS Services chain to resolve the integration and interoperability in distributed GIS environment. Cores of this model are GIS Services chain engine which can realize interoperability between systems or data and workflow engine which can control and monitor the execution of GIS Services chain.4. The research studies several issues of distributed GIS application. For rapid indexing of distributed GIS data, a hierarchical metadata framework is designed to find data in two-step. An efficient processing technology with "clip-piece" is proposed to resolve the massive Remote Sensing image data processing. Finally, based on version mechanism, FGDB (File-GDB) model is designed to realize distributed collaborative editing work.5. By analyzing the existing visual modeling and model description technologies, a new visual modeling based on RDBMS (Relational Database Management System) and extended ECA rules is put forth. The new method advances GIS Services chain modeling, especially in extensibility, consistency maintenance and long transaction. Workflow technology is introduced in the new modeling for automated executing and monitoring of GIS Services chain.6. User-oriented GIS Services evaluation indexes are brought forward for service selection. With reference workflow evaluation model, a hierarchical model is discussed for GIS Services chain evaluation. For low credibility, poor availability of GIS Services in UDDI (Universal Description, Discovery and Integration), the author proposes an idea of feedback based on GIS Services Qos (Quality of Service) to modify the Services metadata.7. With the new requirement of urban planning management, the research designs and implements a prototype system of GIS Services chain which based on the workflow technology. Then the research demonstrates the integrated application model mentioned above and visual modeling based on RDBMS and extended ECA rules. The prototype system verifies the feasibility of combination of GIS Services chain and workflow in distributed GIS application to resolve the integration and interoperability, and the new method in controlling the execution and watch of GIS Services chain.The research shows that the integrated model of GIS Services chain achieves integration and interoperability between heterogeneous data and systems with its loose system architecture, platform-independent and other characteristics. Meanwhile, the introduction of workflow implements the automatic execution, monitoring and tracking. And the separation of business procedure logic and application logic enables subsequent changes to be incorporated into the GIS Services chain, which adapts system to the rapidly change of business. The "two-step" spatial data indexing method based on hierarchical metadata framework, efficient processing technology with "clip-piece" and the FGDB distributed collaborative editing model resolve problems in application, which is beneficial to popularity of GIS Services chain.