A new generation of information systems such as organizational memories, vertical aggregators, infomediaries, etc. is emerging nowadays. Such systems, termed Community Web Portals, intend to support speci c communities of interest (e.g., enterprise, professional, trading) on corporate intranets or the Web. More precisely, Portal Catalogs, organize and describe various information resources (e.g., sites, documents, data) for diverse target audiences (corporate, inter-enterprise, e-marketplace, etc.), in a multitude of ways, which are far more exible and complex than those provided by standard (relational or object) databases. Yet, in commercial software for deploying Community Portals, querying is still limited to full-text (or attribute-value) retrieval and more advanced information-seeking needs implies navigational access. Furthermore, recent Web standards for describing resources are completely ignored. In this paper, we propose a declarative language suitable for querying Portal Catalogs created according to the Resource Description Framework (RDF) W3C standard. Our language, called RQL, relies on a formal graph model, that captures the RDF modeling primitives and permits the interpretation of heterogeneous descriptions by means of one or more schemas. In this context, RQL adapts the functionality of semistructured query languages to the peculiarities of RDF but also extends this functionality in order to uniformly query both resource descriptions and related schemas. Then, RQL enables to query Portal Catalogs holding multipurpose descriptions of community resources while preserving a conceptually uni ed view of the Catalog for (sub-)communities employing di erent RDF schemas. RQL is actually used by several applications aiming at building, accessing and personalizing Community Web Portals. This work was partially supported by the European project C-Web (IST-1999-13479).