Database Reference
In-Depth Information
ontology. Line 4 states the URI for the current ontology and optionally a Version URI.
It is common practice to number the versions of an ontology, but the most up-to-date
version will have an unversioned URI. In this example, we are looking at the most
up-to-date version of the ontology, which is also version 1, hence the two separate
URIs stated on line 4. Lines 5 and 6 state that we are importing the Dublin Core
and Rabbit ontologies into our Administrative Geography ontology, and lines 7-11
are annotations that apply to the whole ontology. It is also possible to annotate a
single entity (i.e., a class or property) or an axiom. Frequently, the
rdfs:label
annotation property is used to annotate each class and property to provide a “human-
friendly” version of the class or property name. For example, while the class name
might be
LicensedEstablishment
as one single word, it would also be labeled
with “Licensed Establishment”—allowing spaces, accents, numbers, or other sym-
bols that are forbidden in OWL class or property names. Good ontology editing tools
are then able to use these labels to provide a more readable view on the ontology,
and an author can use the labels instead of the official names to handle the concepts.
The annotations on lines 7 and 8 use Dublin Core annotation properties to state
who owns the copyright on the ontology and the ontology title, respectively. Lines 9
and 10 state the purpose and scope of the ontology, which are described more in
Chapter 10. Line 11 gives the version number of the ontology. Lines 12-16 state the
annotation properties that are used in this ontology.
Ontology annotations provide metadata to help a user analyze and compare the
ontology to others for mapping and management purposes. They do not provide any
semantic meaning to the ontology and are not included in the reasoning process. As
well as
owl:versionInfo
, OWL DL provides some other constructs for annota-
tion purposes:
owl:backwardCompatibleWith
,
owl:incompatibleWith
,
owl:deprecated
, and
owl:priorVersion
. Built-in annotation properties from
RDFS, which we discussed in Chapter 7, such as
rdfs:label
,
rdfs:comment
,
rdfs:seeAlso
, and
rdfs:isDefinedBy
, can also be used.
9.3.2
c
Lasses
The root class of an OWL ontology is
owl:Thing
, a predefined, universal (set) class
that includes all individuals. Every concept we talk about in the ontology inherits
from this root. Since OWL also incorporates RDFS, an
rdfs:Resource
is a kind
of
owl:Thing
, an
rdfs:Class
is a kind of
rdfs:Resource
(as we already
know), and an
owl:Class
is a kind of
rdfs:Class
. OWL also predefines the
empty class
owl:Nothing
, which has no members. If the results of your reason-
ing end up putting any of your individuals into the
owl:Nothing
class, you have
gone wrong somewhere. The set of classes and statements about classes is known as
the Terminological Box or Tbox. The set of instances or, to use OWL terminology,
Individuals and facts about them is known as the Assertion Box or Abox.
To make the Rabbit statement “Pub is a Concept.” in OWL, we would need to say
Class:Pub
SubClassOf: owl:Thing
