3. Semantic Web languages

A number of specialized languages are at the heart of WS and are its most visible aspect. We summarize their role here, and will return to these languages in a second, more technical and applied article. The approach adopted by the W3C, from a language point of view, has been to take up what has largely contributed to the success of the Web (HTML...): standardized languages whose tagged text files are easily exchangeable and usable by multiple tools. These languages therefore use the Web's already well-accepted standards (URI, XML, namespaces, tags, etc.), which are in a way its lower layers. Figure 2 shows one of the recent versions of the language "cake" created by the W3C, and illustrates the relationship between these different languages by showing the stacking of increasing levels of...