7 Semantic Web Languages

Having defined the Semantic Web infrastructure, which enables the creation of a web of data, two aspects remain to be seen. The first one concerns the rich semantics that were announced as a part of the Semantic Web vision: how can the conceptual knowledge useful for a range of applications be successfully ported to and exploited on the Semantic Web? The second aspect concerns the access to Semantic Web data: how can one query and successfully find the information that is represented on these large RDF graphs that constitute the Semantic Web information sphere? The goal of this chapter is to make the reader familiar with relevant languages that address these two crucial matters: representing conceptual knowledge and querying RDF data. With respect to conceptual knowledge, there exist very expressive languages like OWL, which allow to formally specify the ontologies that guide the creation of RDF data and make it amenable to automated reasoning processes. This will be the object of Section 7.2. However, we will see in section 7.3 that OWL does not meet all conceptual representation requirements. 100 Semantic Web Languages In particular, its high level of formal precision is not appropriate for modeling a wide range o