OWL Web Ontology Language
Overview
W3C
Recommendation 10 February 2004
-
This version:
-
http://www.w3.org/TR/2004/REC-owl-features-20040210/
-
Latest version:
-
http://www.w3.org/TR/owl-features/
-
Previous version:
-
http://www.w3.org/TR/2003/PR-owl-features-20031215/
-
Editors:
-
Deborah L. McGuinness (Knowledge Systems Laboratory,
Stanford University)
-
Frank van Harmelen (Vrije Universiteit, Amsterdam)
Frank.van.Harmelen@cs.vu.nl
Please refer to the errata
for this document, which may include some normative corrections.
See also translations.
Copyright © 2004
W3C®
(MIT,
ERCIM,
Keio), All
Rights Reserved. W3C
liability,
trademark,
document use and
software licensing rules apply.
The OWL Web Ontology Language is designed for use by
applications that need to process the content of information
instead of just presenting information to humans. OWL
facilitates greater machine interpretability of Web content
than that supported by XML, RDF, and RDF Schema (RDF-S) by
providing additional vocabulary along with a formal
semantics. OWL has three increasingly-expressive
sublanguages: OWL Lite, OWL DL, and OWL Full.
This document is written for readers who want a first
impression of the capabilities of OWL. It provides an
introduction to OWL by informally describing the features of
each of the sublanguages of OWL. Some knowledge of
RDF Schema is useful for understanding this document, but
not essential. After this document, interested readers may
turn to the OWL
Guide for more detailed descriptions and extensive
examples on the features of OWL. The normative formal
definition of OWL can be found in the
OWL Semantics
and Abstract Syntax.
Status of this document
-
Introduction
-
Document Roadmap
-
Why OWL?
-
The three sublanguages of OWL
-
The structure of this document
-
Language Synopsis
-
OWL Lite Synopsis
-
OWL DL and OWL Full Synopsis
-
Language Description of OWL Lite
-
OWL Lite RDF Schema Features
-
OWL Lite Equality and Inequality
-
OWL Lite Property Characteristics
-
OWL Lite Property Restrictions
-
OWL Lite Restricted Cardinality
-
OWL Lite Class Intersection
-
OWL Datatypes
-
OWL Lite Header Information
-
OWL Lite Annotation Properties
-
OWL Lite Versioning
-
Incremental Language Description of OWL DL and OWL Full
-
Summary
-
References
-
Acknowledgements
-
Change Log
1. Introduction
This document describes the OWL Web Ontology Language. OWL is
intended to be used when the information contained in
documents needs to be processed by applications, as opposed
to situations where the content only needs to be presented to
humans. OWL can be used to explicitly represent the meaning
of terms in vocabularies and the relationships between those
terms. This representation of terms and their
interrelationships is called an ontology. OWL has more
facilities for expressing meaning and semantics than XML,
RDF, and RDF-S, and thus OWL goes beyond these languages in
its ability to represent machine interpretable content on the
Web. OWL is a revision of the
DAML+OIL web ontology language incorporating lessons
learned from the design and application of DAML+OIL.
1.1 Document Roadmap
The OWL Language is described by a set of documents, each
fulfilling a different purpose, and catering to a different
audience. The following provides a brief roadmap for
navigating through this set of documents:
-
This OWL
Overview gives a simple introduction to OWL by
providing a language feature listing with very brief
feature descriptions;
-
The OWL Guide
demonstrates the use of the OWL language by providing an
extended example. It also provides a
glossary
of the terminology used in these documents;
-
The OWL
Reference gives a systematic and compact (but still
informally stated) description of all the modelling
primitives of OWL;
-
The OWL
Semantics and Abstract Syntax document is the final and
formally stated normative definition of the language;
-
The OWL Web
Ontology Language Test Cases document contains a large
set of test cases for the language;
-
The OWL Use
Cases and Requirements document contains a set of use
cases for a web ontology language and compiles a set of
requirements for OWL.
The suggested reading order of the first four documents is
as given since they have been listed in increasing degree of
technical content. The last two documents complete the
documentation set.
1.2 Why OWL?
The Semantic Web is a vision for the future of the Web in
which information is given explicit meaning, making it easier
for machines to automatically process and integrate
information available on the Web. The Semantic Web will build
on XML's ability to define customized tagging schemes and
RDF's flexible approach to representing data. The first level
above RDF required for the Semantic Web is an ontology
language what can formally describe the meaning of
terminology used in Web documents. If machines are expected
to perform useful reasoning tasks on these documents, the
language must go beyond the basic semantics of RDF Schema.
The OWL Use Cases
and Requirements Document provides more
details
on ontologies, motivates the need for a Web Ontology
Language in terms of
six
use cases, and formulates
design
goals,
requirements and
objectives for OWL.
OWL has been designed to meet this need for a Web Ontology
Language. OWL is part of the growing stack of W3C
recommendations related to the Semantic Web.
-
XML provides a
surface syntax for structured documents, but imposes no
semantic constraints on the meaning of these documents.
-
XML Schema is
a language for restricting the structure of XML documents
and also extends XML with datatypes.
-
RDF is a datamodel for objects ("resources") and
relations between them, provides a simple semantics for
this datamodel, and these datamodels can be represented
in an XML syntax.
-
RDF Schema is a vocabulary for describing properties
and classes of RDF resources, with a semantics for
generalization-hierarchies of such properties and
classes.
-
OWL adds more vocabulary for describing properties and
classes: among others, relations between classes (e.g.
disjointness), cardinality (e.g. "exactly one"),
equality, richer typing of properties, characteristics of
properties (e.g. symmetry), and enumerated classes.
1.3 The three sublanguages of
OWL
OWL provides three increasingly expressive sublanguages
designed for use by specific communities of implementers and
users.
-
OWL
Lite supports those users primarily needing a
classification hierarchy and simple constraints. For
example, while it supports cardinality constraints, it
only permits cardinality values of 0 or 1. It should be
simpler to provide tool support for OWL Lite than its
more expressive relatives, and OWL Lite provides a quick
migration path for thesauri and other taxonomies. Owl
Lite also has a lower formal complexity than OWL DL, see
the
section on OWL Lite in the OWL Reference for further
details.
-
OWL DL
supports those users who want the maximum expressiveness
while retaining computational completeness (all
conclusions are guaranteed to be computable) and
decidability (all computations will finish in finite
time). OWL DL includes all OWL language constructs, but
they can be used only under certain restrictions (for
example, while a class may be a subclass of many classes,
a class cannot be an instance of another class).
OWL DL is so
named due to its correspondence with
description logics, a field of research that
has studied the logics that form the formal foundation of
OWL.
-
OWL
Full is meant for users who want maximum
expressiveness and the syntactic freedom of RDF with no
computational guarantees. For example, in OWL Full a
class can be treated simultaneously as a collection of
individuals and as an individual in its own right. OWL
Full allows an ontology to augment the meaning of the
pre-defined (RDF or OWL) vocabulary. It is unlikely that
any reasoning software will be able to support complete
reasoning for every feature of OWL Full.
Each of these sublanguages is an extension of its simpler
predecessor, both in what can be legally expressed and in
what can be validly concluded. The following set of relations
hold. Their inverses do not.
-
Every legal OWL Lite ontology is a legal OWL DL ontology.
-
Every legal OWL DL ontology is a legal OWL Full ontology.
-
Every valid OWL Lite conclusion is a valid OWL DL
conclusion.
-
Every valid OWL DL conclusion is a valid OWL Full
conclusion.
Ontology developers adopting OWL should consider which
sublanguage best suits their needs. The choice between OWL
Lite and OWL DL depends on the extent to which users require
the more-expressive constructs provided by OWL DL. The choice
between OWL DL and OWL Full mainly depends on the extent to
which users require the meta-modeling facilities of RDF
Schema (e.g. defining classes of classes, or attaching
properties to classes). When using OWL Full as compared to
OWL DL, reasoning support is less predictable since complete
OWL Full implementations do not currently exist.
OWL Full can be viewed as an extension of RDF, while OWL
Lite and OWL DL can be viewed as extensions of a restricted
view of RDF. Every OWL (Lite, DL, Full) document is an RDF
document, and every RDF document is an OWL Full document, but
only some RDF documents will be a legal OWL Lite or OWL DL
document. Because of this, some care has to be taken when a
user wants to migrate an RDF document to OWL. When the
expressiveness of OWL DL or OWL Lite is deemed appropriate,
some precautions have to be taken to ensure that the original
RDF document complies with the additional constraints imposed
by OWL DL and OWL Lite. Among others, every URI that is used as
a class name must be explicitly asserted to be of type
owl:Class (and similarly for properties), every individual must
be asserted to belong to at least one class (even if only
owl:Thing), the URI's used for classes, properties and
individuals must be mutually disjoint. The details of these and
other constraints on OWL DL and OWL Lite are explained in
appendix E
of the OWL Reference.
1.4 The structure of this
document
This document first describes the features in OWL Lite,
followed by a description of the features that are added in
OWL DL and OWL Full (OWL DL and OWL Full contain the same
features, but OWL Full is more liberal about how these
features can be combined).
2. Language Synopsis
This section provides a quick index to all the language
features for OWL Lite, OWL DL, and OWL Full.
In this document, italicized terms are terms in OWL. Prefixes
of rdf: or rdfs: are used when terms are already present in
RDF or RDF Schema. Otherwise terms are introduced by OWL.
Thus, the term rdfs:subPropertyOf indicates that
subPropertyOf is already in the rdfs vocabulary (technically
: the rdfs namespace). Also, the term Class is more
precisely stated as owl:Class and is a term introduced
by OWL.
2.1 OWL Lite Synopsis
The list of OWL Lite language constructs is given below.
|
RDF Schema Features:
|
(In)Equality:
|
Property Characteristics:
|
|
Property Restrictions:
|
Restricted Cardinality:
|
Header Information:
|
|
Class Intersection:
|
Versioning:
|
Annotation Properties:
|
|
Datatypes
|
2.2 OWL DL and Full Synopsis
The list of OWL DL and OWL Full language constructs that are
in addition to or expand those of OWL Lite is given below.
|
Class Axioms:
|
Boolean Combinations of Class Expressions:
|
|
Arbitrary Cardinality:
|
Filler Information:
|
3. Language Description of OWL Lite
This section provides an informal description of the OWL Lite
language features. We do not discuss the specific syntax of
these features (see the
OWL Reference for
definitions). Each language feature is hyperlinked to the
appropriate place in the
OWL Guide for
more examples and guidance on usage.
OWL Lite uses only some of the OWL language features and has
more limitations on the use of the features than OWL DL or
OWL Full. For example, in OWL Lite classes can only be
defined in terms of named superclasses (superclasses cannot
be arbitrary expressions), and only certain kinds of class
restrictions can be used. Equivalence between classes and
subclass relationships between classes are also only allowed
between named classes, and not between arbitrary class
expressions. Similarly, restrictions in OWL Lite use only
named classes. OWL Lite also has a limited notion of
cardinality - the only cardinalities allowed to be explicitly
stated are 0 or 1.
3.1 OWL Lite RDF Schema Features
The following OWL Lite features related to RDF Schema are
included.
-
Class: A class defines a group of individuals
that belong together because they share some properties.
For example, Deborah and Frank are both members of the
class Person. Classes can be organized in a specialization
hierarchy using
subClassOf. There is a built-in most general
class named
Thing that is the class of all individuals and is a
superclass of all OWL classes. There is also a built-in
most specific class named
Nothing that is the class that has no instances and a
subclass of all OWL classes.
-
rdfs:subClassOf: Class hierarchies may be
created by making one or more statements that a class is a
subclass of another class. For example, the class Person
could be stated to be a subclass of the class Mammal. From
this a reasoner can deduce that if an individual is a
Person, then it is also a Mammal.
-
rdf:Property: Properties can be used to state
relationships between individuals or from individuals to
data values. Examples of properties include hasChild,
hasRelative, hasSibling, and hasAge. The first three can be
used to relate an instance of a class Person to another
instance of the class Person (and are thus occurences of
ObjectProperty), and the last (hasAge) can be used to
relate an instance of the class Person to an instance of
the datatype Integer (and is thus an occurence of
DatatypeProperty). Both owl:ObjectProperty and
owl:DatatypeProperty are
subclasses
of the RDF class rdf:Property.
-
rdfs:subPropertyOf: Property hierarchies may be
created by making one or more statements that a property is
a subproperty of one or more other properties. For example,
hasSibling may be stated to be a subproperty of
hasRelative. From this a reasoner can deduce that if an
individual is related to another by the hasSibling
property, then it is also related to the other by the
hasRelative property.
-
rdfs:domain: A domain of a property limits the
individuals to which the property can be applied. If a
property relates an individual to another individual, and
the property has a class as one of its domains, then the
individual must belong to the class. For example, the
property hasChild may be stated to have the domain of
Mammal. From this a reasoner can deduce that if Frank
hasChild Anna, then Frank must be a Mammal. Note that
rdfs:domain is called a global restriction since the
restriction is stated on the property and not just on the
property when it is associated with a particular class. See
the discussion below on property restrictions for more
information.
-
rdfs:range: The range of a property limits the
individuals that the property may have as its value. If a
property relates an individual to another individual, and
the property has a class as its range, then the other
individual must belong to the range class. For example, the
property hasChild may be stated to have the range of
Mammal. From this a reasoner can deduce that if Louise is
related to Deborah by the hasChild property, (i.e., Deborah
is the child of Louise), then Deborah is a Mammal. Range is
also a global restriction as is domain above. Again, see
the discussion below on local restrictions (e.g.
AllValuesFrom) for more information.
-
Individual : Individuals are instances
of classes, and properties may be used to relate one
individual to another. For example, an individual named
Deborah may be described as an instance of the class Person
and the property hasEmployer may be used to relate the
individual Deborah to the individual StanfordUniversity.
3.2 OWL Lite Equality and
Inequality
The following OWL Lite features are related to equality or
inequality.
-
equivalentClass : Two classes may be
stated to be equivalent. Equivalent classes have the same
instances. Equality can be used to create synonymous
classes. For example, Car can be stated to be
equivalentClass to Automobile. From this a reasoner
can deduce that any individual that is an instance of Car
is also an instance of Automobile and vice versa.
-
equivalentProperty: Two properties may be
stated to be equivalent. Equivalent properties relate one
individual to the same set of other individuals. Equality
may be used to create synonymous properties. For example,
hasLeader may be stated to be the equivalentProperty
to hasHead. From this a reasoner can deduce that if X is
related to Y by the property hasLeader, X is also related
to Y by the property hasHead and vice versa. A reasoner can
also deduce that hasLeader is a subproperty of hasHead and
hasHead is a subProperty of hasLeader.
-
sameAs: Two individuals may be stated to be the
same. These constructs may be used to create a number of
different names that refer to the same individual. For
example, the individual Deborah may be stated to be the
same individual as DeborahMcGuinness.
-
differentFrom: An individual may be stated to
be different from other individuals. For example, the
individual Frank may be stated to be different from the
individuals Deborah and Jim. Thus, if the individuals Frank
and Deborah are both values for a property that is stated
to be functional (thus the property has at most one value),
then there is a contradiction. Explicitly stating that
individuals are different can be important in when using
languages such as OWL (and RDF) that do not assume that
individuals have one and only one name. For example, with
no additional information, a reasoner will not deduce that
Frank and Deborah refer to distinct individuals.
-
AllDifferent: A number of individuals may be
stated to be mutually distinct in one AllDifferent
statement. For example, Frank, Deborah, and Jim could be
stated to be mutually distinct using the AllDifferent
construct. Unlike the differentFrom statement above, this
would also enforce that Jim and Deborah are distinct (not
just that Frank is distinct from Deborah and Frank is
distinct from Jim). The AllDifferent construct is
particularly useful when there are sets of distinct objects
and when modelers are interested in enforcing the unique
names assumption within those sets of objects. It is used
in conjunction with
distinctMembers to state that all members of a list are
distinct and pairwise disjoint.
3.3 OWL Lite Property
Characteristics
There are special identifiers in OWL Lite that are used to
provide information concerning properties and their values. The
distinction between ObjectProperty and DatatypeProperty is
mentioned
above in the property description.
-
inverseOf: One property may be stated to be the
inverse of another property. If the property P1 is stated
to be the inverse of the property P2, then if X is related
to Y by the P2 property, then Y is related to X by the P1
property. For example, if hasChild is the inverse of
hasParent and Deborah hasParent Louise, then a reasoner can
deduce that Louise hasChild Deborah.
-
TransitiveProperty: Properties may be stated to
be transitive. If a property is transitive, then if the
pair (x,y) is an instance of the transitive property P, and
the pair (y,z) is an instance of P, then the pair (x,z) is
also an instance of P. For example, if ancestor is stated
to be transitive, and if Sara is an ancestor of Louise
(i.e., (Sara,Louise) is an instance of the property
ancestor) and Louise is an ancestor of Deborah (i.e.,
(Louise,Deborah) is an instance of the property ancestor),
then a reasoner can deduce that Sara is an ancestor of
Deborah (i.e., (Sara,Deborah) is an instance of the
property ancestor).
OWL Lite (and OWL DL) impose the side condition that
transitive properties (and their superproperties) cannot
have a maxCardinality 1 restriction. Without this
side-condition, OWL Lite and OWL DL would become
undecidable languages. See the property axiom section of
the OWL
Semantics and Abstract Syntax document for more
information.
-
SymmetricProperty: Properties may be stated to
be symmetric. If a property is symmetric, then if the pair
(x,y) is an instance of the symmetric property P, then the
pair (y,x) is also an instance of P. For example, friend
may be stated to be a symmetric property. Then a reasoner
that is given that Frank is a friend of Deborah can deduce
that Deborah is a friend of Frank.
-
FunctionalProperty : Properties may be stated
to have a unique value. If a property is a
FunctionalProperty, then it has no more than one value for
each individual (it may have no values for an individual).
This characteristic has been referred to as having a unique
property. FunctionalProperty is shorthand for stating that
the property's minimum cardinality is zero and its maximum
cardinality is 1. For example, hasPrimaryEmployer may be
stated to be a FunctionalProperty. From this a reasoner may
deduce that no individual may have more than one primary
employer. This does not imply that every Person must have
at least one primary employer however.
-
InverseFunctionalProperty: Properties may be
stated to be inverse functional. If a property is inverse
functional then the inverse of the property is functional.
Thus the inverse of the property has at most one value for
each individual. This characteristic has also been referred
to as an unambiguous property. For example,
hasUSSocialSecurityNumber (a unique identifier for United
States residents) may be stated to be inverse functional
(or unambiguous). The inverse of this property (which may
be referred to as isTheSocialSecurityNumberFor) has at most
one value for any individual in the class of social
security numbers. Thus any one person's social security
number is the only value for their
isTheSocialSecurityNumberFor property. From this a reasoner
can deduce that no two different individual instances of
Person have the identical US Social Security Number. Also,
a reasoner can deduce that if two instances of Person have
the same social security number, then those two instances
refer to the same individual.
3.4 OWL Lite Property
Restrictions
OWL Lite allows restrictions to be placed on how
properties can be used by instances of a class. These type (and
the cardinality restrictions in the next subsection) are used
within the context of an
owl:Restriction.
The
owl:onProperty
element indicates the restricted property. The following two
restrictions limit which values can be used while the next
section's restrictions limit how many values can be used.
-
allValuesFrom: The restriction allValuesFrom is
stated on a property with respect to a class. It means that
this property on this particular class has a local range
restriction associated with it. Thus if an instance of the
class is related by the property to a second individual,
then the second individual can be inferred to be an
instance of the local range restriction class. For example,
the class Person may have a property called hasDaughter
restricted to have allValuesFrom the class Woman. This
means that if an individual person Louise is related by the
property hasDaughter to the individual Deborah, then from
this a reasoner can deduce that Deborah is an instance of
the class Woman. This restriction allows the property
hasDaughter to be used with other classes, such as the
class Cat, and have an appropriate value restriction
associated with the use of the property on that class. In
this case, hasDaughter would have the local range
restriction of Cat when associated with the class Cat and
would have the local range restriction Person when
associated with the class Person. Note that a reasoner can
not deduce from an allValuesFrom restriction alone that
there actually is at least one value for the property.
-
someValuesFrom: The restriction
someValuesFrom is stated on a property with respect
to a class. A particular class may have a restriction on a
property that at least one value for that property is of a
certain type. For example, the class SemanticWebPaper may
have a someValuesFrom restriction on the hasKeyword
property that states that some value for the
hasKeyword property should be an instance of the class
SemanticWebTopic. This allows for the option of having
multiple keywords and as long as one or more is an instance
of the class SemanticWebTopic, then the paper would be
consistent with the someValuesFrom restriction.
Unlike allValuesFrom, someValuesFrom does not
restrict all the values of the property to be instances of
the same class. If myPaper is an instance of the
SemanticWebPaper class, then myPaper is related by the
hasKeyword property to at least one instance of the
SemanticWebTopic class. Note that a reasoner can not deduce
(as it could with allValuesFrom restrictions) that
all values of hasKeyword are instances of the
SemanticWebTopic class
3.5 OWL Lite Restricted
Cardinality
OWL Lite includes a limited form of cardinality restrictions.
OWL (and OWL Lite) cardinality restrictions are referred to
as local restrictions, since they are stated on properties
with respect to a particular class. That is, the restrictions
constrain the cardinality of that property on instances of
that class. OWL Lite cardinality restrictions are limited
because they only allow statements concerning cardinalities
of value 0 or 1 (they do not allow arbitrary values for
cardinality, as is the case in OWL DL and OWL Full).
-
minCardinality: Cardinality is stated on a
property with respect to a particular class. If a
minCardinality of 1 is stated on a property with
respect to a class, then any instance of that class will be
related to at least one individual by that property. This
restriction is another way of saying that the property is
required to have a value for all instances of the
class. For example, the class Person would not have any
minimum cardinality restrictions stated on a hasOffspring
property since not all persons have offspring. The class
Parent, however would have a minimum cardinality of 1 on
the hasOffspring property. If a reasoner knows that Louise
is a Person, then nothing can be deduced about a minimum
cardinality for her hasOffspring property. Once it is
discovered that Louise is an instance of Parent, then a
reasoner can deduce that Louise is related to at least one
individual by the hasOffspring property. From this
information alone, a reasoner can not deduce any maximum
number of offspring for individual instances of the class
parent. In OWL Lite the only minimum cardinalities allowed
are 0 or 1. A minimum cardinality of zero on a property
just states (in the absence of any more specific
information) that the property is optional with respect to
a class. For example, the property hasOffspring may have a
minimum cardinality of zero on the class Person (while it
is stated to have the more specific information of minimum
cardinality of one on the class Parent).
-
maxCardinality: Cardinality is stated on a
property with respect to a particular class. If a
maxCardinality of 1 is stated on a property with
respect to a class, then any instance of that class will be
related to at most one individual by that property. A
maxCardinality 1 restriction is sometimes called a
functional or unique property. For example, the property
hasRegisteredVotingState on the class UnitedStatesCitizens
may have a maximum cardinality of one (because people are
only allowed to vote in only one state). From this a
reasoner can deduce that individual instances of the class
USCitizens may not be related to two or more distinct
individuals through the hasRegisteredVotingState property.
From a maximum cardinality one restriction alone, a
reasoner can not deduce a minimum cardinality of 1. It may
be useful to state that certain classes have no values for
a particular property. For example, instances of the class
UnmarriedPerson should not be related to any
individuals by the property hasSpouse. This situation is
represented by a maximum cardinality of zero on the
hasSpouse property on the class UnmarriedPerson.
-
cardinality: Cardinality is provided as a
convenience when it is useful to state that a property on a
class has both minCardinality 0 and
maxCardinality 0 or both minCardinality 1 and
maxCardinality 1. For example, the class Person has
exactly one value for the property hasBirthMother. From
this a reasoner can deduce that no two distinct individual
instances of the class Mother may be values for the
hasBirthMother property of the same person.
Alternate namings for these restricted forms of
cardinality were discussed. Current recommendations are to
include any such names in a front end system. More on this
topic is available on the publicly available webont mail
archives with the most relevant message at
http://lists.w3.org/Archives/Public/www-webont-wg/2002Oct/0063.html.
3.6 OWL Lite Class Intersection
OWL Lite contains an intersection constructor but limits
its usage.
-
intersectionOf: OWL Lite allows intersections
of named classes and restrictions. For example, the class
EmployedPerson can be described as the
intersectionOf Person and EmployedThings (which
could be defined as things that have a minimum cardinality
of 1 on the hasEmployer property). From this a reasoner may
deduce that any particular EmployedPerson has at least one
employer.
3.7 OWL Datatypes
OWL uses the RDF mechanisms for data values.
See the OWL Guide
section
on datatypes for a more detailed description of the
built-in OWL datatypes taken largely from the XML Schema
datatypes.
3.8 OWL Lite Header Information
OWL Lite supports notions of ontology inclusion and
relationships and attaching information to ontologies.
See the
OWL Reference for
details and the
OWL
Guide for examples.
3.9 OWL Lite Annotation
Properties
OWL Lite allows annotations on classes, properties,
individuals and ontology headers. The use of these annotations
is subject to certain restrictions. See the
section on
Annotations in the OWL Reference for details.
3.10 OWL Lite Versioning
RDF already has a small vocabulary for describing
versioning information. OWL significantly extends this
vocabulary. See the
OWL
Reference for further details.
4. Incremental Language Description
of OWL DL and OWL Full
Both OWL DL and OWL Full use the same vocabulary although
OWL DL is subject to some restrictions. Roughly, OWL DL
requires type separation (a class can not also be an individual
or property, a property can not also be an individual or
class). This implies that restrictions cannot be applied to the
language elements of OWL itself (something that is allowed in
OWL Full). Furthermore, OWL DL requires that properties are
either ObjectProperties or DatatypeProperties:
DatatypeProperties are relations between instances of classes
and RDF literals and XML Schema datatypes, while
ObjectProperties are relations between instances of two
classes. The
OWL
Semantics and Abstract Syntax document explains the
distinctions and limitations. We describe the OWL DL and OWL
Full vocabulary that extends the constructions of OWL Lite
below.
-
oneOf: (enumerated classes): Classes can be
described by enumeration of the individuals that make up
the class. The members of the class are exactly the set of
enumerated individuals; no more, no less. For example, the
class of daysOfTheWeek can be described by simply
enumerating the individuals Sunday, Monday, Tuesday,
Wednesday, Thursday, Friday, Saturday. From this a reasoner
can deduce the maximum cardinality (7) of any property that
has daysOfTheWeek as its allValuesFrom restriction.
-
hasValue: (property values): A property can be
required to have a certain individual as a value (also
sometimes referred to as property values). For example,
instances of the class of dutchCitizens can be
characterized as those people that have theNetherlands as a
value of their nationality. (The nationality value,
theNetherlands, is an instance of the class of
Nationalities).
-
disjointWith: Classes may be stated to be
disjoint from each other. For example, Man and Woman can be
stated to be disjoint classes. From this disjointWith
statement, a reasoner can deduce an inconsistency when an
individual is stated to be an instance of both and
similarly a reasoner can deduce that if A is an instance of
Man, then A is not an instance of Woman.
-
unionOf, complementOf, intersectionOf (Boolean
combinations): OWL DL and OWL Full allow arbitrary Boolean
combinations of classes and restrictions: unionOf,
complementOf, and intersectionOf. For example, using
unionOf, we can state that a class contains things that are
either USCitizens or DutchCitizens. Using complementOf, we
could state that children are not SeniorCitizens.
(i.e. the class Children is a subclass of the complement of
SeniorCitizens). Citizenship of the European Union could be
described as the union of the citizenship of all member
states.
-
minCardinality, maxCardinality,
cardinality (full cardinality):
While in OWL Lite, cardinalities are restricted to at
least, at most or exactly 1 or 0, full OWL allows
cardinality statements for arbitrary non-negative integers.
For example the class of DINKs ("Dual Income, No Kids")
would restrict the cardinality of the property hasIncome to
a minimum cardinality of two (while the property hasChild
would have to be restricted to cardinality 0).
-
complex classes : In
many constructs, OWL Lite restricts the syntax to single
class names (e.g. in subClassOf or equivalentClass
statements). OWL Full extends this restriction to allow
arbitrarily complex class descriptions, consisting of
enumerated classes, property restrictions, and Boolean
combinations. Also, OWL Full allows classes to be used as
instances (and OWL DL and OWL Lite do not). For more on
this topic, see the "Design for Use" section of the Guide
document.
This document provides an overview of the Web Ontology
Language by providing a brief introduction to why one might
need a Web ontology language and how OWL fits in with related
W3C languages. It also provides a brief description of the
three OWL sublanguages: OWL Lite, OWL DL, and OWL Full along
with a feature synopsis for each of the languages. This
document is an update to the Feature Synopsis Document. It
provides simple descriptions of the constructs along with
simple examples. It references the
OWL reference
document, the
OWL
Guide, and the
OWL Semantics and
Abstract Syntax document for more details. Previous
versions (
December
15, 2003,
September 5, 2003,
August
18, 2003,
July 30, 2003,
May 1, 2003,
March 20, 2003,
January 2, 2003,
July 29, 2002,
July 8, 2002,
June 23, 2002,
May 26, 2002, and
May 15, 2002) of this document provide the historical view
of the evolution of OWL Lite and the issues discussed in its
evolution.
-
[OWL Guide]
-
OWL Web Ontology Language Guide, Michael K.
Smith, Chris Welty, and Deborah L. McGuinness, Editors, W3C
Recommendation, 10 February 2004,
http://www.w3.org/TR/2004/REC-owl-guide-20040210/ .
Latest
version available at http://www.w3.org/TR/owl-guide/ .
-
[OWL
Reference]
-
OWL Web Ontology Language Reference, Mike Dean
and Guus Schreiber, Editors, W3C Recommendation, 10 February 2004,
http://www.w3.org/TR/2004/REC-owl-ref-20040210/ .
Latest version
available at http://www.w3.org/TR/owl-ref/ .
-
[OWL Abstract
Syntax and Semantics]
-
OWL Web Ontology Language Semantics and Abstract
Syntax, Peter F. Patel-Schneider, Pat Hayes, and
Ian Horrocks, Editors, W3C Recommendation, 10 February 2004,
http://www.w3.org/TR/2004/REC-owl-semantics-20040210/ .
Latest
version available at
http://www.w3.org/TR/owl-semantics/ .
-
[OWL Test]
-
OWL Web Ontology Language Test Cases, Jeremy J.
Carroll and Jos De Roo, Editors, W3C Recommendation, 10 February 2004,
http://www.w3.org/TR/2004/REC-owl-test-20040210/ .
Latest version
available at http://www.w3.org/TR/owl-test/ .
-
[OWL Requirements]
-
OWL Web Ontology Language Use Cases and
Requirements, Jeff Heflin, Editor, W3C
Recommendation, 10 February 2004,
http://www.w3.org/TR/2004/REC-webont-req-20040210/ .
Latest
version available at http://www.w3.org/TR/webont-req/ .
-
[OWL Issues]
-
Web Ontology Issue Status. Michael K.
Smith, ed. 1 November 2003.
-
[DAML+OIL
Reference]
-
DAML+OIL
Reference Description . Dan Connolly, Frank van
Harmelen, Ian Horrocks, Deborah L. McGuinness, Peter F.
Patel-Schneider, and Lynn Andrea Stein. W3C Note 18
December 2001.
-
[XML]
-
Extensible Markup
Language (XML).
-
[XML Schema]
-
XML
Schema .
-
[XML-SCHEMA2]
-
XML
Schema Part 2: Datatypes - W3C Recommendation,
World Wide Web Consortium, 2 May 2001.
-
[RDF/XML Syntax]
- RDF/XML Syntax Specification (Revised), Dave Beckett, Editor, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-syntax-grammar-20040210/ . Latest version available at http://www.w3.org/TR/rdf-syntax-grammar/ .
-
[RDF Concepts]
- Resource Description Framework (RDF): Concepts and Abstract Syntax,
Graham Klyne and Jeremy J. Carroll, Editors, W3C Recommendation, 10
February 2004, http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/ . Latest version available at http://www.w3.org/TR/rdf-concepts/ .
-
[RDF Schema]
- RDF Vocabulary Description Language 1.0: RDF Schema,
Dan Brickley and R. V. Guha, Editors, W3C Recommendation, 10 February
2004, http://www.w3.org/TR/2004/REC-rdf-schema-20040210/ . Latest version available at http://www.w3.org/TR/rdf-schema/ .
-
[RDF Semantics]
- RDF Semantics, Patrick Hayes, Editor, W3C Recommendation, 10 February 2004, http://www.w3.org/TR/2004/REC-rdf-mt-20040210/ . Latest version available at http://www.w3.org/TR/rdf-mt/ .
-
[Description Logics]
-
The
Description Logic Handbook. Franz Baader, Diego
Calvanese, Deborah McGuinness, Daniele Nardi, Peter
Patel-Schneider, editors. Cambridge University Press, 2003;
and Description Logics
Home Page.
This document is the result of extensive discussions within
the Web Ontology
Working Group as a whole. The participants in this
Working Group included: Yasser alSafadi, Jean-François
Baget, James Barnette, Sean Bechhofer, Jonathan Borden,
Frederik Brysse, Stephen Buswell, Jeremy Carroll, Dan
Connolly, Peter Crowther, Jonathan Dale, Jos De Roo, David De
Roure, Mike Dean, Larry Eshelman, Jérôme Euzenat,
Tim Finin, Nicholas Gibbins, Sandro Hawke, Patrick Hayes,
Jeff Heflin, Ziv Hellman, James Hendler, Bernard Horan,
Masahiro Hori, Ian Horrocks, Jane Hunter, Francesco
Iannuzzelli, Rüdiger Klein, Natasha Kravtsova, Ora
Lassila, Massimo Marchiori, Deborah McGuinness, Enrico Motta,
Leo Obrst, Mehrdad Omidvari, Martin Pike, Marwan Sabbouh,
Guus Schreiber, Noboru Shimizu, Michael Sintek, Michael K.
Smith, John Stanton, Lynn Andrea Stein, Herman ter Horst,
David Trastour, Frank van Harmelen, Bernard Vatant, Raphael
Volz, Evan Wallace, Christopher Welty, Charles White, and
John Yanosy.
-
Added owl:Nothing to OWL Lite.
-
Added pointer to last call document under title
-
Changed all links to owl-absyn to owl-semantics
-
Incorporated Lee Lacy's grammatical comments from
public-webont-comments dated April 21, 2003.
-
Incorporated Lee Lacy's other comments: annotation
properties, version properties, and other missing tags in
2.2 (which got reorganised as a result)
-
changed hasOffSpring example to hasDaughter (request of
Morten Frederiksen)
-
incorporated all Lasilla's comment, including replacing
"machine readability" by "machine interpretability" and
various typo's.
-
Added sentence on lower complexity class of OWL Lite, as
proposed by Jim Hendler
-
Added first sentence to section 1, after Sandro Hawke's
comment
-
Restored link to style file
-
Added link to test document and May 1 version
-
Added references section
-
Changed back to relative references to sections
-
Changed links to http://www.w3.org/TR/xx from previous
versions with updates later to ...TR/2003/CR-xx-20030818/
-
Added Change Log since candidate recommendation.
-
Deleted Control Ms at the end of all lines.
-
Incorporated Jeff Rafter's
public webont comments.
-
Updated Status, Document links, date of publication, etc.
according to PR
email from chair.
-
Two broken links fixed - W3C icon was referenced by
referring to local W3c expansion src="OWL Web Ontology
Language Overview_files/ as was gif for author. Added full
expansion to W3C icon (http://www.w3.org/Icons/w3c_home)
and email gif
(http://www.w3.org/2001/sw/WebOnt/guide-src/Email.Deborah.McGuinness.gif).
-
Removed control Ms at the end of every line introduced with
new version transfer.
-
Added links to previous version in December 2003.
-
Updated document taking Lee Lacy's comments dated January
12, 2004. (Comments mostly small editorial changes, cell
spacing change of 30 to 27 in table, ...)
-
Included Benjamin Nowack's editorial comments.
-
Updated Reference format.
