Base Metrics
Base Metrics comprise of simple metrics, like the counting of classes, axioms, objects etc. These metrics show the quantity of ontology elements.
The difference between the count metrics and the total count metrics is, that the total count metrics takes account of imports from other ontologies.
For the base metrics we chose:
Axiom
Axioms are basic statements of an ontology and also the main component, they state what is true in a domain. It is possible to have axioms for classes, properties, datatype definitions, assertions and annotations.
Class
Classes in ontologies are concepts, these classes can contain other classes or individuals. In other words, a class is a set of individuals. In OWL exists a thing-class, which is a universal class, so every user defined class is a subclass of the thing-class. The corresponding metric count the classes, including the thing-class, to create a view on the quantity of classes.
Individuals
Individuals are the instances of the classes, so they represent the actual object of the domain. There are two types of individuals: named- and anonymous individuals. Named individuals have an explicit name and can be used in every ontology for the same object, while anonymous individuals are used local, only in one ontology. This metric counts all instances, one class is able to have a set of instances.
Property
In OWL there are two types of properties:
Object property
Object properties link individuals to individuals.
Data property
Other than the Object properties the Data properties link individuals to data values (literals).
