Table 2 The applied rules for generating conceptual ontology (TBox)

Table patterns

Table without FK

OWL: class

Table with one FK

Table with more than 2 FKs

Tables that contain exactly 2 foreign keys with presence of independent attributes

Binary Relationship table

Tables that contain exactly 2 foreign keys without presence of independent attributes

We create two object properties ( owl:objectProperty) The latter is an inverse of the former

Tables with one FK

Attributes that are FK + NULL + Not UNIQUE

Object Property + Functional Property + Min Cardinality of the inverse property = 1

Attributes that are FK + NOT NULL + NOT UNIQUE

Object Property + Card = 1 + Min Cardinality of the inverse property = 1

Attributes that are FK + NOT NULL + UNIQUE

Object Property + Functional Property + Functional Property for the inverse Property

Attributes that are FK + NOT NULL + UNIQUE + NOT PK (FK is not equal to the PK)

Object Property + Functional Property + Card = 1 + Functional Property for the inverse Property

Attributes

Attribute ( neither PK nor FK)

DatatypeProperty

Attribute + NOT NULL

DatatypeProperty + MinCardinality = 1

Attributes NOT FK + UNIQUE

DatatypeProperty + MaxCardinality = 1

Primary Key

MinCardinality + MaxCardinality = 1 (Cardinality = 1)

Check Constraint

Attribute with constraint with an integer greater than 0

xsd:positiveInteger

CHECK with enumeration

xsd:positiveInteger

CHECK constraint as Value Restriction

Xsd:minInclusive, Xsd:maxInclusive, Xsd:minExclusive, Xsd:maxExclusive

Default constraint

Attribute with Default Value

Owl:hasValue

Inheritance relationship

Two tables share the same primary key

rdfs:subClassOf

Symmetric Relationship

FK is a reference to the same table

owl: SymmetricProperty

Transitive Relationship

FK is a reference to the same table, but now it is accompanied by a trigger ON DELETE CASCADE

OWL:TransitiveProperty

Inheritance relationship improvement

The range of the foreign Key attribute

Owl:AllValuesFrom