OWL Lite

OWL Lite is the most basic of the three OWL sublanguages, supporting classification hierarchies and simple constraints. Additionally, OWL Lite provides the possibility to build up subclass hierarchies and make properties optional, i.e. to impose a cardinality constraint of 0 and 1. The following are the definitions of tags for OWL Lite according to [29] .

OWL Lite RDF Schema Features

• Class: A class defines a group of individuals because they share some properties.

For instance, classes can be organized in a specialization hierarchy using subClassOf.

Besides Thing is a built-in most general class.

• rdfs:subClassOf : A class is a subclass of another class, which can be described by making one or more statements.

• rdf:Property: A property is used to state relationships between individuals.

• rdfs:subPropertyOf : Similar to subClassof, property hierarchies can be created by making one or more statements that a property is a subproperty of one or more other properties.

• rdfs:domain: A domain of a property states the individuals to which the property can be applied.

• rdfs:range: A range of a property states the individuals that the property may have as its value.

• Individual: Individuals are instances of classes, and properties may be used to relate one individual to another

OWL Lite Equality and Inequality

OWL includes features that are related to equality or inequality.

• equivalentClass : Two classes may be stated to be equivalent. Equivalent classes have the same instances and can be used to create synonymous classes.

• equivalentProperty: Two properties may be stated to be equivalent. Equivalent properties relate one individual to the same set of other individuals and may be used to create synonymous properties

• sameAs: A number of different names, which refer to the same individual, can be stated to be the same by using sameAs

• differentFrom: By using differentFrom, individual can be stated to be different from other individuals.

• AllDifferent: A number of individuals may be stated to be mutually distinct in one AllDifferent statement.

OWL Lite Property Characteristics

There are some special identifiers in OWL Lite that are used to provide information concerning properties and their values.

• inverseOf : One property may be stated to be the inverse of another property. If the property P1 is stated to be the inverse of the property P2, then if X is related to Y by the P2 property, then Y is related to X by the P1 property.

• TransitiveProperty: Properties may be stated to be transitive. If a property is transitive, then if the pair (x,y) is an instance of the transitive property P, and the pair (y,z) is an instance of P, then the pair (x,z) is also an instance of P.

• SymmetricProperty: Properties may be stated to be symmetric. If a property is symmetric, then if the pair (x,y) is an instance of the symmetric property P, then the pair (y,x) is also an instance of P.

• FunctionalProperty : Properties may be stated to have a unique value. If a property is a FunctionalProperty, then it has no more than one value for each individual (it may have no values for an individual). This characteristic has been referred to as having a unique property. FunctionalProperty is shorthand for stating that the property’s minimum cardinality is zero and its maximum cardinality is 1.

• InverseFunctionalProperty: Properties may be stated to be inverse functional.

If a property is inverse functional then the inverse of the property is functional.

Thus the inverse of the property has at most one value for each individual. This characteristic has also been referred to as an unambiguous property.

OWL Lite Property Restrictions

How properties can be used by instances of a class can be stated by property restrictions.

There are two restrictions limit which values can be used.

• allValuesFrom: The restriction allValuesFrom is stated on a property with re-spect to a class. It means that this property on this particular class has a local range restriction associated with it. Thus if an instance of the class is related by the property to a second individual, then the second individual can be inferred to be an instance of the local range restriction class.

• someValuesFrom: The restriction someValuesFrom is stated on a property with respect to a class. A particular class may have a restriction on a property that at least one value for that property is of a certain type.

OWL Lite Restricted Cardinality

OWL Lite includes only a limited form of cardinality restrictions because they only allow statements concerning cardinalities of value 0 or 1 (they do not allow arbitrary values for cardinality, as is the case in OWL DL and OWL Full).

• minCardinality: Cardinality is stated on a property with respect to a particular class. If a minCardinality of 1 is stated on a property with respect to a class, then any instance of that class will be related to at least one individual by that property.

This restriction is another way of saying that the property is required to have a value for all instances of the class.

• maxCardinality: Similar to minCardinality, if a maxCardinality of 1 is stated on a property with respect to a class, then any instance of that class will be related to at most one individual by that property. A maxCardinality 1 restriction is sometimes called a functional or unique property.

• cardinality: Cardinality is provided as a convenience when it is useful to state that a property on a class has both minCardinality 0 and maxCardinality 0 or both minCardinality 1 and maxCardinality 1.