In the future spatial data infrastructures environment, GIS applications are expected to be built upon effective sharing and dynamic integration of heterogeneous geospatial data in distributed environment. OGC (Open Geospatial Consortium) web services make the interactions between application systems much easier than before. As more and more geospatial resource available on the internet, recent interest has advanced from information management to data processing in the SOA environment. OGC Web Processing Service (WPS) enables an open interface for online processing of geospatial data. Via the use of OGC web services, the number of geospatial services available in the internet has been rapidly and continuously increasing, how to locate WPS that meets application needs and understand its usage becomes a major challenge to application developers. To facilitate the interoperable use of WPS, we argue that a WPS must unambiguously describe its processing capability with metadata. Furthermore, in order to identify a WPS process, all WPS must register with a unique OGC URN in an SDI environment. In this research, we have developed a metadata model to describe WPS and embedded the metadata into WSDL documents. Users can therefore efficiently search for WPS that meets their demands via the publish-find-bind approach of W3C Web Services. We further implemented a prototype to test the proposed architecture. The results indicate user can therefore locate suitable online geospatial resource by searching registered WSDL documents of WPS. In the meantime, domain data standards helps to alleviate the ambiguities of input and output of WPS, as its predefined xml schemas can provide constant GML FeatureType model of geospatial features involved in WPS. Though still in the preliminary stage, the presented metadata model has demonstrated its potential to establish an interoperable OGC WPS architecture in the future spatial data infrastructures.