In computing, an ontology is a formal specification of a topic. It is used to define a common terminology for a specific subject or domain (for example, e-commerce, medical guidelines, chemistry). Ontologies can be implemented in varied languages. Some of these languages were created, during the 1990s, specifically for implementing ontologies. Other general languages were also used for that task. Recently, a new generation of ontology markup languages has appeared in the context of the Semantic Web, an extension of the World Wide Web in which information is given well-defined meaning, better enabling computers and people to work in cooperation. Ontologies play a key role in the Semantic Web as a way of representing the semantics of documents and enabling the semantics to be used by Web applications and intelligent agents (for example, Web-searching software).