ABSTRACT
This chapter sets out the main concepts of the Web Ontology Language (OWL) and discusses the various options for software tool support. For those used to object-oriented (OO) design and programming methods, it is easy to think that OWL is an OO language or at least OO like. Since OWL ontology is a Resource Description Framework graph, it can be written using many different syntaxes. The chapter discusses the primary tools available for authoring ontologies in OWL and some factors to take into account when choosing ontology editor. OWL classes are sets of individuals, each sharing some common properties but each also unique and varying from its companions. As well as value constraints restricting properties, OWL specifies cardinality constraints: the maximum, minimum, or exact number of values that a property can take when applied to a particular concept.
