Recent advances in the development of Web models, standards and services generate new challenges in the diffusion, usage, and processing of geo-referenced data. This paper introduces an approach for service description applied to Webbased Geographic Information Systems (Web-GIS). Based on existing standards and recommendations of the OGC and W3C, we propose an extension towards a description of Web-GIS services. Combining recent benefits of OWL-S (Ontology Web Language for Service), we introduce a language that describes Web Services properties and capabilities in order to integrate, manipulate and analyze spatio-temporal data. This enrichment of Web-based GIS services is particularly adapted to characterize dataset histories, and allows for a better understanding of the data and services provided from a user point of view.