Formalizing Cross-Parameter Conditions for Geoprocessing Service Chain Validation

Geoprocessing operations offered via web services provide the means for building complex web-based geospatial applications. Often, certain postconditions such as the spatial reference system, bounding box, schema or quality that hold on the output dataset after the execution of a geoprocessing service are determined and derived from the properties of the inputs passed to the service. Further, geoprocesses often hold preconditions that relate to more than one input, such as the requirement that all inputs must have the same schema. Within current process descriptions for geoprocessing operations, such conditions which we call cross-parameter conditions, can not be explicitly specified. In this paper, the author gives an approach to formalize such cross input-output and cross input parameter conditions in a rule-based language. Further, the author proposes an algorithm for deriving pre- and postconditions for a service composition or workflow out of the pre- and postconditions of the services involved, allowing a more automated handling of workflows in general.