Language Feature Comparison (original) (raw)

The following table summarizes differentiating language features available in XML, RDF, DAML+OIL, and OWL. Please send comments/corrections/additions/other feedback to[email protected].

Discussion

• bounded lists
  • rdf:Seq and rdf:Bag don't provide any indication that the list is complete (e.g. "these are 5 children of X" vs. "X is known to have exactly these 5 children")
  • DAML uses a first/rest structure to represent unordered bounded lists, with nil representing the end of the list
  • rdf:parseType="daml:collection" provides a shorthand and RDF syntax compatibility
• cardinality constraints
  • limit the number of statements with the same subject and predicate
  • the Kleene operators ? (0 or 1), * (0+), and + (1+) in XML DTD provide basic cardinality constraints
  • DAML supports cardinality,minCardinality, andmaxCardinality
• class expressions
  • wherever a Class is referenced, DAML+OIL also allows an expression involvingunionOf,disjointUnionOf,intersectionOf, orcomplementOf
• data types
  • RDF Literals are essentially strings
  • DAML+OIL (March 2001) adds XML Schema data types
• defined classes
  • DAML allows new classes to be defined based on property values or other restrictions of an existing class (e.g. Child is a Person with age < 18) or class expressions.
• enumerations
  • XML DTD allows specification of a restricted set of values for a given attribute
  • DAML provides oneOf
• equivalence
  • to support reasoning across ontologies and knowledge bases, DAML supports equivalentTo for classes, properties, and instances
  • additional mapping constructs may be added to future versions of DAML
• extensibility
  • RDF and DAML allow new Properties to used with existing Classes
  • RDF has been used to define DAML+OIL
  • DAML+OIL may similarly be used to define future languages such as DAML-Logic
• formal semantics
  • DAML+OIL semantics have been expressed in bothmodel-theoretic andaxiomatic forms
• inheritance
  • XML Schema attribute groups formalize DTD use of parameter entities in attribute definitions, but this isn't full inheritance
  • RDF and DAML support subClassOf andsubPropertyOf
• inference
  • DAML+OIL constructs such as TransitiveProperty,UnambiguousProperty,inverseOf, anddisjointWith provide additional information for reasoning engines
  • future versions of DAML are expected to support rules, proof-checking, etc.
• local restrictions
  • RDF associates domain and range constraints with a Property
  • DAML allows Restrictions to be associated with a Class/Property pair, e.g. allowing the color property to be used for the Car andEye classes with different domains
• qualified constraints
  • DAML restrictions allow expressions such as "all children of X are of type Person"
  • the DAML propertieshasClassQ,cardinalityQ,minCardinalityQ, andmaxCardinalityQ allow qualified restrictions such as "at most 3 of the children of X are of type Doctor"
• reification
  • RDF and DAML allow a statement to be the subject of another statement
  • reification provides a standard mechanism for recording data sources, timestamps, etc. without intruding on the data model
  • the DAML+OIL semantics do not currently cover reification
  • in its initial discussions on reification, theJoint Committee has found it useful to distinguish "tagging" (making statements about asserted statements, e.g. source, timestamp, etc.) from "quoting" (making statements about unasserted statements)

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