Members of the W3C OWL Working Group have annnounced the release of seven specifications relating to OWL 2, including two First Public Drafts.
OWL 2 extends OWL, a core standard of the Semantic Web, adding new features that users have requested and that software providers are prepared to implement. The OWL Web Ontology Language builds on RDF and RDF Schema and adds more vocabulary for describing properties and classes:
among others, relations between classes (e.g. disjointness), cardinality (e.g. "exactly one"), equality, richer typing of properties, characteristics of properties (e.g. symmetry), and enumerated classes.
The new features in OWL 2 include extra syntactic sugar, additional property and qualified cardinality constructors, extended datatype support, simple metamodelling, and extended annotations. (1) "OWL 2 Structural Specification and Functional-Style Syntax" defines OWL 2 ontologies in terms of their structure, and it also defines a functional-style syntax in which ontologies can be written. It describes the conceptual structure of OWL 2 ontologies and thus provides a normative abstract model for all (normative and nonnormative) syntaxes of OWL 2. Such a structural specification of OWL 2 provides the foundation for the implementation of OWL 2 tools such as APIs and reasoners. (2) "OWL 2 Direct Semantics"
provides the direct model-theoretic semantics for OWL 2, which is compatible with the description logic SROIQ; urthermore, this document defines the most common inference problems for OWL 2. (3) "OWL2 RDF-Based Semantics" is a first public working draft which provides the RDFS-compatible model-theoretic semantics for OWL 2, called "OWL 2 Full".
A strong relationship holds between the RDF-Based Semantics of OWL 2 Full and the Direct Semantics of OWL 2 DL, in that OWL 2 Full is, in some sense, able to reflect all logical conclusions of OWL 2 DL.
(4) "OWL 2 Mapping to RDF Graphs" provides mappings by means of which every OWL 2 ontology in the functional-style syntax specification can be mapped into RDF triples and back without any change in the formal meaning of the ontology. (5) "OWL 2 XML Serialization" defines an XML syntax for OWL 2 that mirrors its structural specification; an XML schema defines this syntax and is available as a separate document, as well as being included; it declares an XML Serialization Namespace for OWL 2 (http://www.w3.org/ns/owl2-xml). (6) "OWL 2 Web Ontology Language:
Profiles" provides a specification of several profiles of OWL 2 which can be more simply and/or efficiently implemented. In logic, profiles are often called fragments. Most profiles are defined by placing restrictions on the syntax of OWL 2. These restrictions have been specified by modifying the productions of the functional-style syntax.
(7) The "OWL 2 Conformance and Test Cases" first public working draft describes the conditions that OWL 2 tools must satisfy in order to be conformant with the language specification. It also presents a set of tests that both illustrate the features of the language and can be used for testing conformance.