Semantic Web Stack

The Semantic Web Stack, also known as Semantic Web Cake or Semantic Web Layer Cake, illustrates the architecture of the Semantic Web. The Semantic Web is a collaborative movement led by international standards body the World Wide Web Consortium (W3C). The standard promotes common data formats on the World Wide Web. By encouraging the inclusion of semantic content in web pages, the Semantic Web aims at converting the current web, dominated by unstructured and semi-structured documents into a "web of data". The Semantic Web stack builds on the W3C's Resource Description Framework (RDF). The Semantic Web Stack is an illustration of the hierarchy of languages, where each layer exploits and uses capabilities of the layers below. It shows how technologies that are standardized for Semantic Web are organized to make the Semantic Web possible. It also shows how Semantic Web is an extension (not replacement) of classical hypertext web. The illustration was created by Tim Berners-Lee. The stack is still evolving as the layers are concretized. (Note: A humorous talk on the evolving Semantic Web stack was given at the 2009 International Semantic Web Conference by James Hendler.) As shown in the Semantic Web Stack, the following languages or technologies are used to create Semantic Web. The technologies from the bottom of the stack up to OWL are currently standardized and accepted to build Semantic Web applications. It is still not clear how the top of the stack is going to be implemented. All layers of the stack need to be implemented to achieve full visions of the Semantic Web. The bottom layers contain technologies that are well known from hypertext web and that without change provide basis for the semantic web. Internationalized Resource Identifier (IRI), generalization of URI, provides means for uniquely identifying semantic web resources. Semantic Web needs unique identification to allow provable manipulation with resources in the top layers. Unicode serves to represent and manipulate text in many languages.