Asynchronous Geoprocessing Services: An Interoperable Approach

The growth of massive distributed geospatial data and complex geoprocessing algorithms brings complexity to geoprocessing services. One is the asynchronous geoprocessing. The Open Geospatial Consortium (OGC) provides a series of standards and specifications including Web Processing Services (WPS) in advancing interoperability of geospatial web services. Most of them are based on synchronous protocol. Synchronous protocol is not enough to satisfy more complex geoprocessing tasks, especially those in the Sensor Web environment. The OGC Web Notification Service (WNS), an OGC notification and communication service, can send asynchronous notification messages when a client request is accomplished. It can be used with other services for asynchronous notification. This paper presents an interoperable approach for asynchronous geoprocessing services by leveraging WPS and WNS to support asynchronous invocation. We analyze general asynchronous communication patterns on message transfer and invocation available in a Service Oriented Architecture. Compared to existing poll-based approaches, the paper adopts the push pattern for asynchronous notification, while at the same time makes requests standard-compatible. The push pattern is implemented using WNS. An asynchronous adapter for WPS service, combined with WNS, is used for augmenting existing synchronous WPS services with asynchrony. The approach is compatible with existing WPS specification, thus still follows the interoperable service standards in the geospatial domain.