What is OWL?

Web Ontology Language (OWL) is for processing information on the web which is the exact description of the web information and their relationships between web information. It is built on top of RDF. It is also written in XML for simplification of communication between different types of computers with different operating systems and / or application languages. OWL is designed to provide a common way to process the content of the web information so it can be read and understood by computer applications and it is not designed for being displayed to people on the web. Also, OWL is also part of the W3C’s Semantic Web Activity: Web information has exact meaning, Web information can be understood and processed by computers, and computers can integrate information from the web. OWL pretty much will have almost all the characteristics of RDF but it is a sturdy and more robust language with greater machine interpretability than RDF. It has a larger vocabulary and stronger syntax than RDF. OWL falls into the same W3C standard which is the W3C recommendation for the web communities (Wikipedia 2008, W3 schools 2008 and W3C OWL 2008).

Looking at OWL and the three sublanguages:

• OWL Lite – supports those users primarily needing a classification hierarchy and simple constraint features. For example, while OWL Lite supports cardinality constraints, it only permits cardinality values of 0 or 1. It should be simpler to provide tool support for OWL Lite than its more expressive relatives, and provide a quick migration path for thesauri and other taxonomies.
• OWL DL (includes OWL Lite) - supports those users who want the maximum expressiveness without losing computational completeness (all entailments are guaranteed to be computed) and decidability (all computations will finish in finite time) of reasoning systems. OWL DL includes all OWL language constructs with restrictions such as type separation (a class can not also be an individual or property, a property can not also be an individual or class). OWL DL is so named due to its correspondence with description logics [Description Logics], a field of research that has studied a particular decidable fragment of first order logic. OWL DL was designed to support the existing Description Logic business segment and has desirable computational properties for reasoning systems.
• OWL Full (includes OWL DL) - is meant for users who want maximum expressiveness and the syntactic freedom of RDF with no computational guarantees. For example, in OWL Full a class can be treated simultaneously as a collection of individuals and as an individual in its own right. Another significant difference from OWL DL is that a owl:DatatypeProperty can be marked as an owl:InverseFunctionalProperty. OWL Full allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary. It is unlikely that any reasoning software will be able to support every feature of OWL Full.