Untangling Domain Concepts in Ontology Design Patterns
Group (2008)
Available from eprints.soton.ac.uk
or
Abstract
To assist ontology developers modeling complex domain concepts, a comparative analysis of two Ontology Design Patterns (ODPs) has been carried out. As a result, terminology is introduced to characterize certain role and reusability scenarios of class hierarchies in ODPs. An example that benefits from this study is provided.
Author-supplied keywords
Available from eprints.soton.ac.uk
Page 1
Untangling Domain Concepts in Ontology Design Patterns
Introduction
Motivation
Characterizing Role and Reusability
Summary
Whose “Fault” is This?
Untangling Domain Concepts in Ontology Design Patterns
Bene Rodriguez-Castro Hugh Glaser
Dependable Systems and Software Engineering Group
Intelligence, Agents, Multimedia Group
School of Electronics and Computer Science
University of Southampton, UK
June 1st-5th, 2008
1st KRRSW Workshop at the 5th ESWC
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Whose “Fault” is This?
Untangling Domain Concepts in Ontology Design Patterns
Bene Rodriguez-Castro Hugh Glaser
Dependable Systems and Software Engineering Group
Intelligence, Agents, Multimedia Group
School of Electronics and Computer Science
University of Southampton, UK
June 1st-5th, 2008
1st KRRSW Workshop at the 5th ESWC
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 2
Introduction
Motivation
Characterizing Role and Reusability
Summary
Outline
1 Introduction
Ontologies and Ontology Design Patterns (ODPs)
2 Motivation
The ReSIST Network of Excellence
The Fault Domain Concept
3 Characterizing Role and Reusability
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Outline
1 Introduction
Ontologies and Ontology Design Patterns (ODPs)
2 Motivation
The ReSIST Network of Excellence
The Fault Domain Concept
3 Characterizing Role and Reusability
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 3
Introduction
Motivation
Characterizing Role and Reusability
Summary
Ontologies and Ontology Design Patterns (ODPs)
Ontology Design Patterns (ODPs)
Ontologies have emerged as one of the key components
for the realization of the Semantic Web.
Ontology Engineering involves a broad range of activities
focused on the development of ontologies.
Ontology Design Patterns (ODPs) have evolved from the
preceding success of design patterns in software
engineering, (and known as “archetypal solutions to design
problems in a certain context”).
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Ontologies and Ontology Design Patterns (ODPs)
Ontology Design Patterns (ODPs)
Ontologies have emerged as one of the key components
for the realization of the Semantic Web.
Ontology Engineering involves a broad range of activities
focused on the development of ontologies.
Ontology Design Patterns (ODPs) have evolved from the
preceding success of design patterns in software
engineering, (and known as “archetypal solutions to design
problems in a certain context”).
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 4
Introduction
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
The ReSIST Project
The ReSIST Knowledge Base: an ontologically mediated
web portal that enables the end-user to browse and search
different type of information in the area of resilient systems.
(http://www.rkbexplorer.com/explorer/)
The ReSIST Knowledge Base features an ontology in the
field of resilient computing.
The representation of the Fault domain concept in the
ontology for ReSIST is challenging due to:
The complexity of its definition.
The number of roles that it supports in the ontology.
The relationships with other domain concepts in the
ontology.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
The ReSIST Project
The ReSIST Knowledge Base: an ontologically mediated
web portal that enables the end-user to browse and search
different type of information in the area of resilient systems.
(http://www.rkbexplorer.com/explorer/)
The ReSIST Knowledge Base features an ontology in the
field of resilient computing.
The representation of the Fault domain concept in the
ontology for ReSIST is challenging due to:
The complexity of its definition.
The number of roles that it supports in the ontology.
The relationships with other domain concepts in the
ontology.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 5
Introduction
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
Matrix representation of Fault from (Avizienis 2004)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
Matrix representation of Fault from (Avizienis 2004)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 6
Introduction
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
Tree representation of Fault from (Avizienis 2004)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
The ReSIST Network of Excellence
The Fault Domain Concept
Tree representation of Fault from (Avizienis 2004)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 7
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
ODP1: Pattern 2-Variant 2 in (Rector 2005)
Representing Specified Values in OWL: “value partitions” and
“value sets”
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
ODP1: Pattern 2-Variant 2 in (Rector 2005)
Representing Specified Values in OWL: “value partitions” and
“value sets”
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 8
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
ODP2: Approach 4 in (Noy 2005)
Representing Classes As Property Values on the Semantic
Web
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
ODP2: Approach 4 in (Noy 2005)
Representing Classes As Property Values on the Semantic
Web
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 9
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Similarities between the 2 ODPs examined
Both use a hierarchy of classes to provide anonymous
individuals as property values for other concepts in the
ontology
In Pattern 2-Variant 2 from (Rector 2005) the hierarchy is
used as a representation of features, attributes, or
modifiers that describe other concepts in the ontology.
In Approach 5 from (Noy 2005) the hierarchy is used as a
subject index to annotate other domain concepts in the
ontology.
Both keep ontology expressivity within OWL-DL
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Similarities between the 2 ODPs examined
Both use a hierarchy of classes to provide anonymous
individuals as property values for other concepts in the
ontology
In Pattern 2-Variant 2 from (Rector 2005) the hierarchy is
used as a representation of features, attributes, or
modifiers that describe other concepts in the ontology.
In Approach 5 from (Noy 2005) the hierarchy is used as a
subject index to annotate other domain concepts in the
ontology.
Both keep ontology expressivity within OWL-DL
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 10
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Differences between the 2 ODPs examined
Regarding the hierarchy of classes:
In Pattern 2-Variant 2 (Rector 2005) it conforms to the
definition of value partition.
In Approach 4 (Noy 2005) it does not and classes could be
organized in any hierarchical structure.
Regarding the anonymous individuals:
In Pattern 2-Variant 2 (Rector 2005) they are of the same
type of the other individuals in the class.
In Approach 4 (Noy 2005) they are of different type of the
other individuals in the class. Anonymous individuals are
subjects while the others are actual animals.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Differences between the 2 ODPs examined
Regarding the hierarchy of classes:
In Pattern 2-Variant 2 (Rector 2005) it conforms to the
definition of value partition.
In Approach 4 (Noy 2005) it does not and classes could be
organized in any hierarchical structure.
Regarding the anonymous individuals:
In Pattern 2-Variant 2 (Rector 2005) they are of the same
type of the other individuals in the class.
In Approach 4 (Noy 2005) they are of different type of the
other individuals in the class. Anonymous individuals are
subjects while the others are actual animals.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 11
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
A Terminology for Roles of Domain Concepts I
Generic Class Hierarchy (GCH): refers to a set of classes
organized in any hierarchical structure (e.g. a single class
or a set of classes organized in a list, a tree or a directed
acyclic graph).
Domain Class Hierarchy (DCH): refers to any GCH that
contains the classes corresponding to the domain
concepts that the ontology is intended to represent.
Value Class Hierarchy (VCH): refers to any GCH that is
used to provide anonymous individuals as values to
properties for other domain concepts in the ontology.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
A Terminology for Roles of Domain Concepts I
Generic Class Hierarchy (GCH): refers to a set of classes
organized in any hierarchical structure (e.g. a single class
or a set of classes organized in a list, a tree or a directed
acyclic graph).
Domain Class Hierarchy (DCH): refers to any GCH that
contains the classes corresponding to the domain
concepts that the ontology is intended to represent.
Value Class Hierarchy (VCH): refers to any GCH that is
used to provide anonymous individuals as values to
properties for other domain concepts in the ontology.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 12
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
A Terminology for Roles of Domain Concepts II
Value Partition Class Hierarchy (VPCH): refers to a GCH
that: a) is a Value Class Hierarchy and b) conforms to the
definition of a value partition
Domain Concept Space (DCS): identifies the subset of
the ontology model that contains all the classes that
belong to a Domain Class Hierarchy.
Value Space (VS): identifies the subset of the ontology
model that contains all the classes that belong to a Value
Class Hierarchy or Value Partition Class Hierarchy.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
A Terminology for Roles of Domain Concepts II
Value Partition Class Hierarchy (VPCH): refers to a GCH
that: a) is a Value Class Hierarchy and b) conforms to the
definition of a value partition
Domain Concept Space (DCS): identifies the subset of
the ontology model that contains all the classes that
belong to a Domain Class Hierarchy.
Value Space (VS): identifies the subset of the ontology
model that contains all the classes that belong to a Value
Class Hierarchy or Value Partition Class Hierarchy.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 13
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example 1: Roles of Domain Concepts in (Rector
2005)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example 1: Roles of Domain Concepts in (Rector
2005)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 14
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example 2: Roles of Domain Concepts in (Noy 2005)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example 2: Roles of Domain Concepts in (Noy 2005)
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 15
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Scenario 1
Scenario 1:
Let us consider two ontologies O1 and O2, with two
Domain Class Hierarchies DCH1 and DCH2 in their
Domain Concept Space respectively.
In the context of (Noy 2005) and (Rector 2005) we can
reuse DCH2 from O2 to support the role of a Value Class
Hierarchy in ontology O1.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Scenario 1
Scenario 1:
Let us consider two ontologies O1 and O2, with two
Domain Class Hierarchies DCH1 and DCH2 in their
Domain Concept Space respectively.
In the context of (Noy 2005) and (Rector 2005) we can
reuse DCH2 from O2 to support the role of a Value Class
Hierarchy in ontology O1.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 16
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 1: Premise
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 1: Premise
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 17
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 1: Conclusion
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 1: Conclusion
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 18
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Scenario 2
Scenario 2:
Let us consider a single ontology O1, with two Domain
Class Hierarchies DCH11 and DCH12 in its Domain
Concept Space.
In the context of (Noy 2005) and (Rector 2005) we can
reuse DCH12 to support the role of a Value Class
Hierarchy for DCH11 in O1.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Scenario 2
Scenario 2:
Let us consider a single ontology O1, with two Domain
Class Hierarchies DCH11 and DCH12 in its Domain
Concept Space.
In the context of (Noy 2005) and (Rector 2005) we can
reuse DCH12 to support the role of a Value Class
Hierarchy for DCH11 in O1.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 19
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 2: Premise
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 2: Premise
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 20
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 2: Conclusion
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Example Scenario 2: Conclusion
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 21
Introduction
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Representation of Fault in ReSIST fits Scenario 2
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Comparative Analysis of 2 ODPs
Roles of Domain Concepts in ODPs
Reusability of Domain Concepts in ODPs
Role and Reusability of Fault in ReSIST
Representation of Fault in ReSIST fits Scenario 2
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 22
Introduction
Motivation
Characterizing Role and Reusability
Summary
Summary
Performed a comparative analysis of 2 ODPs.
Characterized the role of domain concepts in the 2 ODPs
examined.
Characterized two reusability scenarios for domain
concepts in ODPs.
Made explicit certain potentially implicit modeling decisions
previously taken in ontology building.
Applied findings to the representation of the Fault domain
concept in the ontology for ReSIST.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Summary
Performed a comparative analysis of 2 ODPs.
Characterized the role of domain concepts in the 2 ODPs
examined.
Characterized two reusability scenarios for domain
concepts in ODPs.
Made explicit certain potentially implicit modeling decisions
previously taken in ontology building.
Applied findings to the representation of the Fault domain
concept in the ontology for ReSIST.
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 23
Introduction
Motivation
Characterizing Role and Reusability
Summary
Thanks!!!
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Motivation
Characterizing Role and Reusability
Summary
Thanks!!!
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 24
Appendix References
References I
A. Avizienis, J.-C. Laprie, B. Randell, and C. Landwehr.
Basic Concepts and Taxonomy of Dependable and Secure
Computing.
IEEE Transactions on Dependable and Secure Computing.
01(1):11–33, 2004.
EU Sixth Framework Programme (FP6)
The ReSIST Network of Excellence.
Contract: IST 4 026764 NOE, 2005–2008
http://www.resist-noe.eu/
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
References I
A. Avizienis, J.-C. Laprie, B. Randell, and C. Landwehr.
Basic Concepts and Taxonomy of Dependable and Secure
Computing.
IEEE Transactions on Dependable and Secure Computing.
01(1):11–33, 2004.
EU Sixth Framework Programme (FP6)
The ReSIST Network of Excellence.
Contract: IST 4 026764 NOE, 2005–2008
http://www.resist-noe.eu/
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
Page 25
Appendix References
References II
N. Noy.
Representing Classes As Property Values on the Semantic
Web.
W3C Note, 2005.
http://www.w3.org/TR/2005/
NOTE-swbp-classes-as-values-20050405
A. Rector.
Representing specified values in owl: “value partitions” and
“value sets”.
W3C Note, 2005.
http://www.w3.org/TR/2005/
NOTE-swbp-specified-values-20050517
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
References II
N. Noy.
Representing Classes As Property Values on the Semantic
Web.
W3C Note, 2005.
http://www.w3.org/TR/2005/
NOTE-swbp-classes-as-values-20050405
A. Rector.
Representing specified values in owl: “value partitions” and
“value sets”.
W3C Note, 2005.
http://www.w3.org/TR/2005/
NOTE-swbp-specified-values-20050517
Bene Rodriguez-Castro, Hugh Glaser Whose “Fault” is This?
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