Define Properties o Often interleaved with the previous step o The semantics of subclassof demands that whenever a is a subclass of b, every property statement that holds for instances of B must also apply to instances of A It makes sense to attach properties to the highest class in the hierarchy to which they apply 11 Chapter 7 A Semantic Web primer
11 Chapter 7 A Semantic Web Primer Define Properties ⚫ Often interleaved with the previous step ⚫ The semantics of subClassOf demands that whenever A is a subclass of B, every property statement that holds for instances of B must also apply to instances of A – It makes sense to attach properties to the highest class in the hierarchy to which they apply
Define Properties(2) o While attaching properties to classes, it makes sense to immediately provide statements about the domain and range of these properties o There is a methodological tension here between generality and specificity Flexibility(inheritance to subclasses) Detection of inconsistencies and misconceptions 12 Chapter 7 A Semantic Web primer
12 Chapter 7 A Semantic Web Primer Define Properties (2) ⚫ While attaching properties to classes, it makes sense to immediately provide statements about the domain and range of these properties ⚫ There is a methodological tension here between generality and specificity: – Flexibility (inheritance to subclasses) – Detection of inconsistencies and misconceptions
Define Facets: From rdFs to OWL o Cardinality restrictions ● Required values owl: hasvalue owl:allvalues from owl:some values From e Relational characteristics symmetry, transitivity, inverse properties functional values 13 Chapter 7 A Semantic Web primer
13 Chapter 7 A Semantic Web Primer Define Facets: From RDFS to OWL ⚫ Cardinality restrictions ⚫ Required values – owl:hasValue – owl:allValuesFrom – owl:someValuesFrom ⚫ Relational characteristics – symmetry, transitivity, inverse properties, functional values
Define Instances o Filling the ontologies with such instances is a separate step e Number of instances > number of classes o Thus populating an ontology with instances is not done manually Retrieved from legacy data sources(DBS) Extracted automatically from a text corpus 14 Chapter 7 A Semantic Web primer
14 Chapter 7 A Semantic Web Primer Define Instances ⚫ Filling the ontologies with such instances is a separate step ⚫ Number of instances >> number of classes ⚫ Thus populating an ontology with instances is not done manually – Retrieved from legacy data sources (DBs) – Extracted automatically from a text corpus