Study Of Key Technology In Geospatial Information Sharing Platform Based On Grid Services

After entering into 21st century, the urgent affairs for survey changing from digitization to information is that the construction of NSDI in our country must be pushed quickly, and sharing and application of Geospatial Information industry have to be accelerated. Grid technology provides a new technical way for solving geospatial information sharing and service mode on base of taking resources sharing totally and the integrated management as an objective.In recent years, "Service" becomes a focal concept for implementing resources encapsulation and conformity in network environment. Along with Web services technology popularized gradually, Web services has been become first choice technology for realizing the "service". The further sharing and conformity of service resource is realized by service composition based on business process, so the stronger and moreintegrated service was provided. With the promoting of new architecture of Grid------Web Services ResourceFrame, Web Services and Grid Services have been converging increasingly, and the compatibility and unification of both standards and specification are realized. By using grid services, we can encapsulate the complicated geospatial information-processing course, and deploy it in the network or grid environment according to unified standard descriptive service interface, thus geospatial information is obtained easily by accessing grid services. Therefore in this article grid services and the service composition technology are used as basic method for constructing the geospatial information-sharing platform.At present, study on Web service combination has been already launched, but owing to lack of the effective service combination frame model and the corresponding model analysis technology, the study on modeling and analysis for service composition is imperfect; on the side, the current related geography space grid service classification can not satisfy demand of service combination based on business flow, so we should expand the classification from the function and semantic granularity. This study is launched aiming at shortages above-mentioned, and main research achievements are as follows:(1) GIS-LM is designed and put forward based on SOA construct and layered service model. This model is divided into six layers from bottom to up, in turn: Base Resource layer, Data Sharing Layer, Basic Software Layer, Basic Service Layer, Grid Services Composition Layer and Application Services Layer. Every layer is encapsulated by using grid services, and grid services are integrated by ESB. It is classified by grid source layer,grid service layer and grid application based on logical function. GIS-LM emphasizes the integrating oriented to SOA, which is the basic frame for geospatial information sharing platform based on grid services.(2) Geospatial services composition model—ServiceWF has been constructed based on WF_Net. This model applies WF_Net to business flow logic description of service combination. In this model transaction indicates grid service and place indicates service composition rules or composition logical judgment, so the validity of process description of this model is fully ensured. At the same time, four basic service composition relations are put forward. They are sequence composition, parallel composition, conditional composition and repeat composition, which are the basic logical rules for composing services. These four relations can be used across and repeatedly, to meet need of complex function of geospatial service composition.(3) The present situation of geospatial information service classification was analyzed and summarized. Grid services are subdivided according to geospatial information processing task and functional semantic granularity, and the geospatial information processing semantic was described in detail.(4) Service composition based on business flow is implemented by applying WS-BPEL. At the same time, three implementation modes: services composition template, composition template builder and services template designer were brought forward, and their applicable scopes were analyzed. (5) Grid services composition support testing system is implemented and designed based on Oracle ADF and Java EE5.0, and the test antetype was constructed.