Metadata and the Semantic Web - Web Standards: Mastering HTML5, CSS3, and XML - page 245

Knowledge Organization Systems: Schemas, Vocabularies,
and Ontologies
Taxonomies or controlled vocabularies are structured collections of terms that can be used as metadata element values.
They are parts of conceptual data schemas (conceptual data models) that map concepts and their relationships. The
namespaces reveal the meaning of tags and attributes and form vocabularies . Formalized conceptual structures can be
defined as ontologies , in other words, knowledge representations of sets of concepts in a domain and the relationships
between them. Web ontologies make it possible to describe complex statements in any topic in a machine-readable
format.
Namespaces provide a mechanism to extend the vocabulary of markup languages. To use external vocabularies
and ontologies of various metadata technologies, the XML namespace facility is applied in order to associate all
properties with the appropriate schema that defines them. Specific metadata can be provided this way such as friends
of the author, the nearest airport to the author, GPS coordinates of the office, and so on. User-defined namespaces
(schemas) can be created for additional classes and instances of resources.
Shorthand notations are used throughout the Semantic Web to reduce document length. A popular mechanism
is called the qualified name ( Qname ), which is applied in XML, XML Schema, RDF, RDF Schema, OWL, Dublin Core,
and so on. The following are the most common Qnames:

dc
Refers to the namespace URI http://purl.org/dc/elements/1.1/

•

owl
Refers to the namespace URI http://www.w3.org/2002/07/owl#

•

rdf
Refers to the namespace URI http://www.w3.org/1999/02/22-rdf-syntax-ns#

•

rdfs
Refers to the namespace URI http://www.w3.org/2000/01/rdf-schema#

•

xsd
Refers to the namespace URI http://www.w3.org/2001/XMLSchema#

•

The selection of Semantic Web applications is increasing. For example, OntosMiner runs ontology-driven
multilingual information extraction and provides the output in various formats, including RDF(S), XML, OWL,
and N3 [71]. Clinical archetypes can be represented and managed as web ontologies in OWL. OWL can also be
applied for e-government representations. Web ontologies can be applied for considering viewpoints of learning
resources such as online programming courses [72]. Financial headline news can also be represented by
ontologies [73]. The following is a short list of some of the more established knowledge organization systems:

• Functional Requirements for Bibliographic Records , often abbreviated as FRBR , can be used to
express bibliographic records with properties such as creator , part , embodiment , successor ,
and subject . FRBR has four classes: Work , Expression , Manifestation , and Item [74].

• Licenses of creative works can be denoted by Creative Commons . The Creative Commons

Rights Expression Language is ideal to describe copyright in RDF. It has properties such as
permits , requires , prohibits , jurisdiction , legalcode , and deprecatedOn , as well as the
classes Work , License , Jurisdiction , Permission , Requirement , and Prohibition [75].

• The Open Digital Rights Language is an open standard for policy expressions and is being

developed and promoted by the ODRL Initiative [76]. The digital management of rights performed
using ODRL has also caught attention, and ODRL is also described as a W3C Note [77].