=Paper=
{{Paper
|id=Vol-184/paper-16
|storemode=property
|title=Annotating OWL Ontologies
|pdfUrl=https://ceur-ws.org/Vol-184/semAnnot04-16.pdf
|volume=Vol-184
|dblpUrl=https://dblp.org/rec/conf/semweb/ParsiaK04
}}
==Annotating OWL Ontologies==
https://ceur-ws.org/Vol-184/semAnnot04-16.pdf
Annotating OWL Ontologies
Bijan Parsia and Aditya Kalyanpur
University of Maryland, MIND Lab, 8400 Baltimore Ave,
College Park MD 20742, USA
{bparsia}@isr.umd.edu
{aditya}@cs.umd.edu
1 Introduction
One key function of the Semantic Web is to support knowledge representation
based annotations of Web “resources”. The linguistic apparatus (e.g., OWL1 )
used to express these annotations (e.g., OWL classes, or properties) are them-
selves Web resources and hence subject to annotation. To this end, we have
integrated Annotea2 based human and machine oriented annotations into our
OWL ontology editor SWOOP.3
2 OWL Entities and Annotation Properties
OWL has four sorts of entity that are of primary interest to an annotator or
ontology user: ontologies themselves, classes, properties, and individuals. In the
DL species of OWL, the expressiveness of the language for describing each sort
of entity varies greatly, from the wide range of constructors and sorts of axioms
for defining classes to the minimal vocabulary (with minimal logical impact) for
describing ontologies themselves. By contrast, the Full species of OWL allows
for the entire language to be used for any sort of entity.
OWL DL does have one sort of assertion which can be uniformly applied to
all sorts of OWL entity: owl:AnnotationProperty45 based assertions. From the
model theoretic point of view, such assertions are mere comments. All annota-
tion properties are ignored by the reasoner, and they may not themselves be
structured by further axioms.6 owl:AnnotationProperty assertions can have as
objects either individuals or datavalues, including rdf:XMLLiterals, thus can em-
bed arbitrary XML, including RDF/XML (e.g., Annotea comments), XHTML,
or SVG. The built in annotation properties rdfs:label and rdfs:comment are al-
ready extensively used in user interfaces (e.g., tool tips) and in other end user
displays.
1
The W3C’s Web Ontology Language: http://www.w3.org/2001/sw/WebOnt/
2
http://www.w3.org/2001/Annotea/
3
http://www.mindswap.org/2004/SWOOP/
4
In this paper, the ‘rdf’,‘rdfs’, and ‘owl’ are mapped to the obvious namespaces.
5
http://www.w3.org/TR/owl-ref/#Header
6
OWL DL is probably more restricted than it needs to be. For example, some form
of subproperty reasoning over annotation properties is quite feasible.
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3 Annotea for OWL
The Annotea project developed an infrastructure for the creation and sharing
of out of band, fine grained, extensible, Web based annotations. The Annotea
framework has two parts: an RDF based annotation format and a protocol for
publishing, retrieving, and managing those annotations. We have extended the
Annotea format to support machine oriented annotations for collaborative edit-
ing. We have also investigated other distribution mechanisms such as OWL an-
notation properties and RSS 1.0 feeds.
We have written an Annotea client plugin for SWOOP. The SWOOP plugin
can publish and display annotations using the standard Annotea vocabulary
(including support for various annotation types such as questions, explanations,
examples, etc.) to the Annotea server or to an annotation property in an OWL
document.
We have also defined an OWL ontology for a new class of annotations — on-
tology changes. The Annotea project did define a “Change” class of annotations,
but it is designed to indicate a proposed change to the annotated document, with
the proposal described by a chunk of HTML-marked-up natural language. In our
ontology, annotations correspond to specific edits (assertions, deletions, modifi-
cations) made in SWOOP and SWOOP can read and apply those edits .
SWOOP uses the OWL API7 to model ontologies and their associated enti-
ties. The OWL API separates the representation of changes from the application
of changes. Each possible change type has a corresponding Java class in the API,
which are subsequently applied to the ontology (essentially, the Command de-
sign pattern). These classes allow for the rich representation of changes, includ-
ing metadata about the changes. We have used these classes as the basis for our
changes annotations. Using this change’ ontology, SWOOP can externalize and
export annotated change sets, which can then be browsed, filtered, endorsed,
recommended, and selectively accepted. Thus, it is possible to define “virtual
versions” of an ontology by specifying a base ontology and a set of changes to
apply to it.8
4 Granularity
Annotea uses XPointer9 to associate annotations with fine grained parts of doc-
uments. For classes, properties, and individuals, there isn’t a lot of further gran-
ularity to be had. The URI of a class gets you that class and classes do not
have subranges. Class descriptions, as collections of axioms, have an interest-
ing and fine grain, while as collections of RDF triples they have an even finer
grain, though of disputed use. We plan to explore XPointer schemes10 which
address the definitions. It is likely that we will focus above the triple layer, i.e.,
on axioms.
7
http://owl.man.ac.uk/api.shtml
8
This mechanism is modeled on Smalltalk’s change records and sets.
9
http://www.w3.org/TR/xptr/
10
http://www.mindswap.org/papers/swrp-iswc04.pdf
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