13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 1 OWL Lite: Ch. 13- Property Characteristics Atilla ELÇİ

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 2 Property Characteristics To provide additional detail info on properties beyond their declaration Metaproperties (properties of properties) and classes for general statements about properties: –Global property restrictions –Relating properties –Inference shortcuts –Local property restrictions

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 3 Global Property Restrictions In order to restrict all uses of a property These are: –Those provided by RDFS: rdfs:domain rdfs:range. –Functional property –Inverse functional property

13 Dec Rev. 29/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 4 Global Property Restrictions (continued) Functional Property (owl:FunctionalProperty): –A functional property can have at most a unique value for a particular subject individual, that is, no value or one value only. That is, a particular item may not have a price (if the property has not been stated for it) or can have only one value for hasPrice property. –Implications: If a reasoner finds a value for a functional property of a subject, it stops looking for more! If a validating software (such as Prolog program testing a case question) finds more than one value, that indicates that the assertion has created an illegal condition. => Assertions are not valid! If an individual has two items (different URIRefs) for value for a functional property, then these items are the same.

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 5 Global Property Restrictions (continued) Inverse Functional Property (owl:InverseFunctionalProperty): –Opposite relationship of a functional property is an inverse functional property. –Identifies object properties whose values uniquely identify the subject instance of a property. In typed node syntax: That is, a value of hasIDNumber relation identifies one particular (a unique) subject. –Implications: If a reasoner finds two URIrefs that identify resources with the same value for an OWL inverse functional property, it means that the two are referencing the same resource. Inverse of an inverse functional property is functional!

13 Dec Rev. 23/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 6 Relating Properties Property equivalence (owl:equivalentProperty): –Equivalent properties relate the same subject resource to the same value (object resource) where both are properties). Ex.: where menuPrice & menuCost are equivalenced. –Subclass of owl:sameAs & rdfs:subPropertyOf property. –Good for “merging” ontologies by combining their symbol tables without actually combining the ontology documents. –Applies on any rdf:Property and returns an rdf:Property instance.

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 7 Relating Properties (continued) Inverse Property (owl:inverseOf Property): –An inverse property relates a value (in the range) of a property back to its domain: just like the derefencing in C/C++. Ex.: Means that the ingredient having this property is used in a dish Means that the dish having this property uses an ingrediant Refined Sugar Turkish Baklava –A reasoner than infers that: –Note that inverseOf is symmetric! –Applies on any owl:ObjectProperty and returns an owl:ObjectProperty instance.

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 8 Inference Shortcuts OWL statements in aid of inference engines: membership in predefined Transitive/Symmetric Object Property classes. Transitive Property (owl:TransitiveProperty): –Means same as in math: A A<C. This example implies that compKanteen < central. –NB: there are several restrictions on the use of transitive property in OWL Lite: no local/global cardinality contraint on themselves, their inverses, or their superproperties; No functional/inverse functional designation; Domain & range must match in use (see ex above); Applies only on owl:ObjectProperty instances.

13 Dec Rev. 30/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 9 Inference Shortcuts (continued) Symmetric Property (owl:SymmetricProperty): –A symmetric property also relates values back to subject resources, that is, it implies a relationship in the opposite direction. Tel Kadayif Turkish Kaymak –A reasoner than infers that :kadayif :goesWellWith :cream. –NB: there are restrictions on the use of symmetric property in OWL Lite: If the domain and range of a symmetric property are restricted, they must be the same.

13 Dec. 2006CmpE 583 Fall 2006 OWL Lite- Property Char’s. 10 Local Property Restrictions owlRestriction: –Used to apply a property restriction to a particular class extension rather than all classes. –Can be of: owl:onProperty Value restriction Cardinality restriction

13 Dec Rev. 29/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 11 Local Property Restrictions (continued) owlRestriction / owl:onProperty: –onProperty property identifies the object property or datatype property being restricted. Another property is used to mark the specific kind of restriction. ”> –The two types of local restrictions are: Property value restriction Property cardinality restriction.

13 Dec Rev. 29/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 12 Local Property Restrictions (continued) Value contraints: –Used to further and individually restrict the range of a property. –The Universal quantifier: owl:allValuesFrom: The universal quantifier takes a class expression or datatype. –The Existential Quantifier: owl:someValuesFrom: At least one value of the restricted property must be an instance of the specified class.

13 Dec Rev. 29/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 13 Local Property Restrictions (continued) Cardinality contraints: Used to restrict the number of values a property should have for subject members from a particular subject description. The value of a cardinality constraint is restricted to 0 or 1 in OWL Lite meaning that: –0: to prohibit the use of a property or limit the number of occurrences. –1: to require a property or limit the number of occurrences. Minimum cardinality (owl:minCardinality): –Example: in stating an optional item: 0 –Example: in stating absolute requirement of an item: 1

13 Dec Rev. 29/12/08 CmpE 583 Fall 2006 OWL Lite- Property Char’s. 14 Local Property Restrictions (continued) Cardinality contraints (continued) : Maximum cardinality (owl:maxCardinality): –Example: in stating an absolute maximum of values for a class’s property: 0 Absolute cardinality (owl:Cardinality): –May be used as shorthand for min/max cardinality. In OWL Lite only 0/1 is allowed. For a summary of various cardinality features and purpose of use, please refer to Table 13-5 Using Appropriate Cardinality Statements and Values and Table 16.2 OWL Lite Restriction Summary