First, I introduce basic terminologies that will be used for the discussion. These definitions are adopted from W3C OWL Reference Guide.
Class: A class defines a group of individual that belong together because they share some properties. Two related concepts defined in OWL are “Thing” and “Nothing”
Thing: Thing comes as a predefined vocabulary of OWL. It is the superclass of all classes and a default class of all individuals. Thus, every individual in OWL world is a member of class Thing (or owl:Thing)
Nothing: Nothing (or owl: Nothing) is a class that has no instances and is a subclass of all classes.
Individuals: Individuals are instances of classes, and properties may be used to relate one individual to another
Property: Property is a binary relation that states relationships between individuals or from an individual to data value. Property can be further distinguished as “ObjectTypeProperty” or “DataTypeProperty”.
ObjectTypeProperty (owl:ObjectTypeProperty): It is defined as the relation between instances of two classes
DataTypeProperty (owl:DataTypeProperty) : It is defined as the relation between instances of classes and literal values such as string, number, and date.
RDF Resource: RDF resource is described in RDF document as anything that has a valid unique resource identifier (or URI). Hereafter, it is referred as “resource”.
The differences between the three sublanguages are due to differences in the definition of owl:class and owl:ObjectPropertyType in the three sublanguages of OWL
1. Owl:class vs rdfs:class
In OWL full, owl:class is defined as equivalent to rdfs:class. Thus any class that is a subclass of rdfs:class is also a subclass of owl:class. As a result, any valid rdf document can be considered as a valid OWL full document.
In constrast to owl full, owl:class is defined as subclass of rdfs:class in Lite and DL. Thus not all classes of RDF document (that are subclass of rdfs:class) can be an instances or subclasses of owl:class. As a result, a valid rdf document cannot be considered as a valid OWL Lite or DL document.
2. Owl:ObjectTypeProperty and rdf:Property
In OWL full, owl:ObjectTypeProperty is considered equivalent to rdf:Property. As a result, owl:DataTypeProperty, which is a subclass of rdf:property, is also a subclass of owl:ObjectTypeProperty. Thus, any property in OWL that is defined as datatype can also be interpreted as objectype property. This provides much of the expressiveness in OWL full.
Again in constrast to OWL full, owl:DataTypeProperty and owl:ObjectTypeProperty are defined as disjoint subclasses of rdf:property. As a result, built-in relations such as “InverseOf”, “InverseFunctional”, “Symmertric”, and “Transitive” cannot be specified as datatype property. This is because a dataType property defines a relation from one individual to a literal (integer, number, date). Thus, inverse of dataType Property does not hold much meaning.
These differences in the definitons of owl:class, owl:objectypeproperty, owl:datatypeproperty are the main reasons for the differences in OWL Lite, DL, and Full. Table 1 provides a comparison between these three sublanguages. Certain examples are included to show what can/cannot be expressed.
|Theoretically,no rdf document can be assumed to be compatible with OWL Lite||Theoretically,no rdf document can be assumed to be compatible with OWL DL||All valid rdf documents are OWL full|
|Restrictions on class definition||Requires separation of classes, instances, properties, and data values||Requires separation of classes, instances, properties, and data values||Classes
can be instances or properties at the same time. For example, it is perfectly legal in OWL Full to have a “Fokker-100” identifier which acts both as a class name
(denoting the set of Fokker-100 airplanes flying around the world) and as an individual name (e.g., an instance of the class
mixing of rdf and owl constructs
mixing of RDF and OWL constructs
|Freely allows mixing of RDF and OWL constructs|
|The only class description available in OWL lite is IntersectionOf||Classes
can be described as UnionOf , ComplementOf, IntersectionOf, and enumeration
Eg: class can be exhaustively defined by its instances. For example defining a class DaysOfWeek exhaustively by Sun, Mon, Tue, Wed, Thurs,
|Classes can be UnionOf, ComplementOf, IntersectionOf, and enumeration Eg:
class can be exhaustively defined by its instances. For example defining a
class DaysOfWeek exhaustively by Sun, Mon, Tue, Wed, Thurs, Fri, Sat
|Cardinality Constraints||Cardinality: 0/1 MinCardinality: 0/1 MaxCardinality: 0/1||Cardinality>= 0 MaxCardinality >= 0
MinCardinality >= 0
|Cardinality>= 0 MaxCardinality >= 0
MinCardinality >= 0
|Value Constraints||owl:allValuesFrom Owl:someValuesFrom Object type for owl:valueFrom should be a class name or class identifier||Owl:allValuesFrom Owl:someValueFrom Owl:hasValue||Owl:allValuesFrom Owl:someValueFrom Owl:hasValue|
not allow metamodeling
|Does not allow metamodeling||Allows metamodeling. Thus RDF and OWL constructs can be augmented or redefined|
|Class||OWL:class is subclass of RDFS:class||OWL:class is subclass of RDFS:class.||RDFS:class and OWL:class are equivalent|