On querying geospatial and georeferenced metadata resources in G-Portal

G-Portal is a Web portal system providing a range of digital library services to access geospatial and georeferenced resources on the Web. Among them are the storage and query subsystems that provide a central repository of metadata resources organized under different projects. In G-Portal, all metadata resources are represented in XML (Extensible Markup Language) and they are compliant to some resource schemas defined by their creators. The resource schemas are extended versions of a basic resource schema making it easy to accommodate all kinds of metadata resources while maintaining the portability of resource data. To support queries over the geospatial and georeferenced metadata resources, a XQuery-like query language known as RQL (Resource Query Language) has been designed. We present the RQL language features and provide some experimental findings about the storage design and query evaluation strategies for RQL, queries.