A brief introduction to the Semantic Web Technologies
Semantic Web Technologies are a set of ideas, approaches and standards, leading to the future of WWW. Idea of Semantic Web, authored by Tim Berners-Lee, is to shift from hypertext-based Internet to semantic-based information representation on the websites. The basic principle of semantic encoding says that any information may be expressed as a set of structured statements using "subject - predicate - definition" pattern. Such statement is called "triple". One triple tells us one fact, for example "John Smith was born 01.01.1970". The subject of a triple always an information object, referred by URI. Predicate represents a link between subjects, or a property of certain subject. Definition may be either an object referred by URI, or a literal. Any information may be represented as a set of triples.
Computer software must have a dictionary, describing every type of subjects and predicates, to process triple-encoded data. Such schema is named ontology. There is a set of standards describing syntax for represents ontology and triples:
RDF – syntax for representing triples. RDF statements may be expressed using XML or Turtle syntax.
RDFS – RDF schema definition language, a subset of OWL.
OWL – ontology definition language.
SPARQL – triple-based database technology, allowing create triple stores, and query them using structured query language.
Micro-formats is one of useful usages for Semantic Web technologies. Using micro-formats, web sites may provide contact information, goods indexes etc. Search engines are able to "understand" this information and provide a user with useful tools based on data semantics.
Micro-formats are using rather small and particular ontologies. Beside them, there are big and "universal" ontologies developed, such as "Dublin Core". Some ontologies are adopted as standards for particular industries, such as petroleum. Developers may use and extend these ontologies for their particular needs.