异步地理信息网络处理服务方法研究

An Approach to Asynchronous Geoprocessing Service

随着海量分布式地理空间数据的持续增长和地理空间处理服务复杂程度的不断增加,异步地理空间信息服务已经成为当前地理空间信息领域的研究热点。开放地理信息联盟(Open GIS Consortium,OGC)针对地理空间信息服务互操作制定的一系列标准规范大多建立在同步协议之上,适用于较为简单的非实时计算环境,难以满足复杂、动态的异步信息处理需求。本文提出了一种异步网络处理服务实现方法,以网络处理服务(Web processing service,WPS)和网络通知服务(Web notification service,WNS)为核心,扩展了标准的网络处理服务请求,从而支持异步调用。

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.