An Approach to Asynchronous Geoprocessing Service

The growth of massive distributed geospatial data and complex geoprocessing services makes asynchronous geoprocessing a research hotspot in the geospatial domain. Meanwhile, the Open Geospatial Consortium (OGC) provides a series of standards and specifications to advance interoperability between geospatial Web services. Most are based on synchronous protocols that cannot satisfy more complex geoprocessing tasks, especially those in the Sensor Web environment. This paper presents an interoperable approach for asynchronous geoprocessing services that leverages Web processing services (WPSs) and Web notification services (WNSs) to support asynchronous invocation. We analyze the general asynchronous communication patterns in message transfer and invocation available in a service oriented architecture. Compared to existing poll-based approaches, the paper adopts a push pattern for asynchronous notification, and at the same time makes user requests standard-compatible. The push pattern was implemented using WNS. An asynchronous adapter for WPS services, combined with a WNS, is used for augmenting existing synchronous WPS services with asynchrony. The approach is compatible with existing WPS specifications, thus still follows the interoperable service standards in the geospatial domain. A service prototype was designed and implemented, and performance tests are discussed.