Languages for the Semantic Web
by
Peter F. Patel-Schneider
Semantic Web Tower
Semantic Web Tower (from Tim Berners-Lee)
Elements of the Semantic Web Tower
XML - eXtensible Markup Language
, including namespaces
XML Schema
RDF - Resource Description Framework
RDF Schema
DAML+OIL
, an ontology language
other elements do not yet exist
new ontology language (OWL) under development
XML
XML in 10 points
"XML is for structuring data"
XML (now) has a relatively firm form and meaning (
XML 1.0 Recommendation
)
XML has extra pieces, like
XML Schema
"XML is the basis for RDF and the Semantic Web"
XML Schema
"XML Schemas express shared vocabularies"
XML Schemas "provide a means for defining the structure, content, and semantics of XML documents"
XML Schema provides
a set of data types, and methods for defining new data types
methods for defining structures, consisting of data types
methods for associating structures and data types with XML constructs
XML Schemas are written in XML, but the meaning of XML Schemas is
not
related to the meaning of XML.
RDF
RDF is "a foundation for processing metadata"
RDF is the language for the semantic web
RDF had
a syntax and a data model
RDF is now getting
a better syntax
and
model theory
RDF can be written in XML, but the meaning of RDF is
not
related to the meaning of XML
RDF Schema
RDF Schema provides mechanisms for defining RDF vocabularies
RDF Schema extends the type system of RDF to
define classes and properties and inclusion relationships between them
define domains and ranges for properties
RDF Schema is written in RDF, and the meaning of RDF Schema is an extension of the meaning of RDF
DAML+OIL
DAML+OIL provides a richer set of constructs for defining classes and properties and their relationships
DAML+OIL allows classes
to have complete definitions
be enumerations
to locally restrict properties in various ways
DAML+OIL provides properties that are
transitive
functional
inverse functional
DAML+OIL uses RDF syntax, but does
not
use the RDF model theory
