GrOWL: a graphical syntax for OWL-DL
Classes
Classes are represented as ovals, like in the RDF/Graph syntax
owl:Thing and owl:Nothing are represented by diamonds labelled with the corresponding
DL symbols (top and bottom)
Taxonomies and concepts mapping
Subclass: owl:subClassOf, is an (empty) arrow with the subclass symbol
Equivalence: two equivalent classes are connected by an undirected link with an
equivalence symbol
Disjunction: two disjuncted classes are connected through an undirected link with the
“not” label
Example: Dog and Cat are disjoint subclasses of Animal. Class Cane is equivalent to
class Dog.
Boolean composition of classes
Logical operators (and restrictions) define anonymous concepts, so they have a
stereotype similar to the one for basic classes (or concepts). They are represented by
circles decorated with the specific constructor.
Each operator is linked to its arguments through unlabelled oriented links. The number of
links depends on the arity of the represented operator.
From the example:
 Person = Man OR Woman
 Woman = Person AND Female
 Woman = Person AND NOT Man
Object Properties
Properties are represented by horizontal segments with arrows at the ends
Functional properties: have one single arrow on the right. In the example gender is
functional
Inverse functional properties: the filler is a “key” for the entoty, like the login in the
example
Transitive properties: have a “+” in the upper right
Symmetric properties: have a bidirectional arrow in the upper left part. In the example
“friend” is symmetric
Role axioms
Domain / range: concepts and roles are connected by “empty arrows” following the
direction domain->property->range. In the example gender goes from Animal to Gender.
Hierarchies and equivalences: can be represented with the same stereotypes used for
class hierarchies
Inverse role: two inverse roles are connected with an undirected link with the “-” symbol.
In the example “knownBy” is the inverse of “knows” (and vice versa)
Restrictions
SomeValuesFrom: is the set of individual with at least one filler for a giver property . It is
represented with a circle with the existential operator inside. It is connected to the role
and the concept.
In the example a driver is exactly whoever owns at least one driving license.
AllValuesFrom: is the set of individuals having all the filler of a given property belonging
to a given concept
In the example: a candidate must get only good marks
Cardinality: MaxCardinality / MinCardinality / Cardinality: are labelled with the
cardinality sign and limit.
In the example:
 Monogamous = <=1 spouse
 Polygamous = >=2 spouse
 Bigamous = =2 spouse
Hybrid restrictions
Operators that involve individuals to define concepts:
OneOf: defines the concept as the set of its instances. In the example Gender contains
only “m” and “f”.
HasValue: defines the concept given an individual the instances nust be related to.
In the example any instance of Female bust have “f” as gender
ABox Assertions
Individuals are represented as rectables with the URI of the resource.
Individual types are represented connecting it to correspondent classes with links
labelled with “belongs” symbol.
Individuals can be connected with arrows reporting the name of roles to represent role
instances.
In the example: marco and luca are persons and are friends
Individual equalities and inequalities can be stated connecting individuals with links
labelled with diamonds. In the example “monday” is different from “tuesday” and is equal
to “lunedi”.
AllDifferent can be applied to reduce the number of triples and is represented by a
“circled” version of different operator. In the example “monday”, “tuesday” , “wednesday”
and “thursday” are distrinct.
DataTyp e Properties
DataType Properties follow the same rules of object properties, but they are dashed.
Literal types are represented by dashed oval.
In the example the name is a datatype property from Person to literals of type xsd:string
Literal values are inserted into dashed rectangles.
Dataytype properties instances connect individuals to literals.
In the example: the individual x has name “Mario”
Literal types can be defined by enumeration. Stereotype is the same of the oneOf
construct (but dashed being a literal).
In the example, a salutation can be “mr”, “miss”, “mrs”, or “Dr.”