Semantic Web Languages and Semantic Markup

Today’s World Wide Web is primary composed of web pages with information displayed in natural language text and images, for humans to view and understand. Machines are only used to display the information either on screen or in printed format. The idea behind the semantic web is to add markup to the web page so that the meaning of the content can be captured and then encoded in a form that a machine can understand.

Tim Berners-Lee, the creator of the World Wide Web, envisioned the architecture of the Semantic Web as having many layers as depicted in his famous “Layer Cake”. Each layer depicts a language and each layer progressing up the “Layer Cake” is a language of increasing power. XML and RDF are the foundational languages which the Semantic Web is built. RDFS is an ontology/knowledge representation language and is the underlying mechanism for new web ontology languages such as DARPA Agent Markup Language (DAML), Ontobroker, Ontology Inference Layer (OIL), DAML-ONT and DAML+OIL and more recently Ontology Web Language (OWL). All of these languages support defining shared data models.

It is important that web pages begin to show more of a formal structure. Web pages are usually HTML documents although some XML documents exist. Presentation information needs to be separate from the structured document so semantics can be drawn from the webpage and the actual content of the web page can be read and understood by the knowledgebase (agents). Semantic markup is a way to describe data that uses the terminologies defined by one or more ontologies. The ontologies standardize and provide interpretations of web content.

Different semantic web languages allow different levels of expression. Most languages allow ontology classifications and the definitions for each class to be defined. In some cases, a form of logic is allowed. RDF is the most restrictive language, allowing links for defining categories and properties and links for applying domain and range constraints. SHOE allows simple logic rules to define relationships not possible in RDF. OIL allows description logic and allows web designers to define different types of definitions. DAML+OIL allows rules to be defined but also allows refinement for defining constraints and relationships among resources, as well as set operations and transitivity rules. OWL, the most expressive of all, adds additional vocabulary and increased formal semantics, a more robust typing of properties, and enumerated classes.

Our Focus

Because RDF and RDFS are foundational languages, and OWL is the most expressive of the Semantic Languages, we, at Mathis Webs, specialize in RDF, RDFS and OWL. We will work with you to design and redefine your website to take advantage of the advanced capabilities of the Semantic Web.