OWL 2 Web Ontology Language
New Features and Rationale

W3C Working Draft 11 June 2009

This version:

http://www.w3.org/TR/2009/WD-owl2-new-features-20090611/

Latest version:

http://www.w3.org/TR/owl2-new-features/

Previous version:

http://www.w3.org/TR/2009/WD-owl2-new-features-20090421/ (color-coded diff)

Editors:

Christine Golbreich, University of Versailles Saint-Quentin and LIRMM

Evan K. Wallace, National Institute of Standards and Technology (NIST)

Contributors:

Peter F. Patel-Schneider, Bell Labs Research, Alcatel-Lucent

This document is also available in these non-normative formats: PDF version.

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Copyright © 2009 W3C^® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.

Abstract

Status of this Document

May Be Superseded

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

Summary of Changes

Last Call

The Working Group believes this document is now essentially done, so this is a "Last Call" draft. The document is not expected to change significantly, going forward.

Please Comment By 30 July 2009

The OWL Working Group seeks public feedback on this Working Draft. Please send your comments to public-owl-comments@w3.org (public archive). If possible, please offer specific changes to the text that would address your concern. You may also wish to check the Wiki Version of this document and see if the relevant text has already been updated.

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Patents

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This document provides an overview of the main new features of OWL 2 and their rationale. These features were determined based on real applications and user and tool-developer experience, some of which has been documented in the OWLED Workshop Series. The inclusion of the features is supported by use cases provided to the W3C OWL Working Group, some of which are listed in the Section 7. This document also describes and motivates some of the other design decisions that were made during the development of OWL 2 or purposefully retained from OWL Web Ontology Language (OWL 1), particularly the various concrete syntaxes for OWL 2, and the relationship of OWL 2 with RDF (Section 4). OWL 2 extends OWL 1 and inherits the language features, design decisions, and use cases for OWL 1. This document thus forms an extension of the Use Cases and Requirements that underlie OWL 1 [OWL Use Cases and Requirements].

OWL 2 adds several new features to OWL 1, including increased expressive power for properties, extended support for datatypes, simple metamodeling capabilities, extended annotation capabilities, and keys (Section 2). OWL 2 also defines several profiles – OWL 2 language subsets that may better meet certain performance requirements or may be easier to implement (Section 3).

2.1.1 F1: DisjointUnion

While OWL 1 provides means to define a set of subclasses as a disjoint and complete covering of a superclass by using several axioms, this cannot be done concisely.

DisjointUnion defines a class as the union of other classes, all of which are pairwise disjoint. It is a shorthand for separate axioms making the classes pairwise disjoint and one setting up the union class. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #1 Use Case #2 Use Case #3 Use Case #4

2.1.2 F2: DisjointClasses

While OWL 1 provides means to state that two subclasses are disjoint, stating that several subclasses are pairwise disjoint cannot be done concisely.

DisjointClasses states that all classes from the set are pairwise disjoint. It is a shorthand for binary disjointness axioms between the classes. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #1 Use Case #2

2.1.3 F3: NegativeObjectPropertyAssertion and NegativeDataPropertyAssertion

While OWL 1 provides means to assert values of a property for an individual, it does not provide a construct for directly asserting values of a property that an individual does not have (negative facts).

NegativeObjectPropertyAssertion (resp. NegativeDataPropertyAssertion) states that a given property does not hold for the given individuals. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #9

2.2.1 F4: Self Restriction

OWL 1 does not allow defining subclasses of objects that are related to themselves by a given property, for example the subclass of processes that auto-:regulate themselves. This local reflexivity is useful in many applications, particularly when global reflexivity does not hold for a property in general, but local reflexivity holds for a subset. The OWL 2 construct ObjectHasSelf allows asserting local reflexivity. Self restrictions are part of SROIQ [SROIQ], an extension of the description logic underlying OWL-DL (SHOIN) designed to provide additions requested by users, while not affecting its decidability and practicability. SROIQ has been supported by several reasoners, including FACT++ [TOOLS].

A class expression defined using an ObjectHasSelf restriction denotes the class of all objects that are related to themselves via the given object property. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #5 Use Case #3

While OWL 1 allows defining restrictions on the number of instances of a property, e.g. for defining persons that have at least three children, it does not provide means to restrain the class or data range of its instances (qualified cardinality restrictions), e.g. for specifying the class of persons that have at least three children who are girls. In OWL 2, both qualified or unqualified cardinality restrictions are possible. Qualified object and data cardinality are present in SROIQ and have been successfully implemented. They are already supported by various tools and reasoners (e.g.; Protégé 4, FACT++, PELLET, RACER, KAON2) [TOOLS] [OWL API].

ObjectMinCardinality, ObjectMaxCardinality, and ObjectExactCardinality (DataMinCardinality, DataMaxCardinality, and DataExactCardinality) allow asserting minimum, maximum or exact qualified cardinality restrictions, object (respectively, data) properties. Normative Syntax Direct Semantics RDF-Based Semantics

• Object Property Cardinality Restrictions

• Data Property Cardinality Restrictions

Use Case #1 Use Case #2 Use Case #3, Use Case #4 Use Case #8

2.2.3 F6: Reflexive, Irreflexive, and Asymmetric Object Properties

While OWL 1 allows to assert that an object property is symmetric or transitive, it is impossible to assert that the property is reflexive, irreflexive or asymmetric.

The OWL 2 construct ReflexiveObjectProperty allows asserting that an object property expression is globally reflexive - that is the property holds for all the individuals. Normative Syntax Direct Semantics RDF-Based_Semantics

The OWL 2 construct IrreflexiveObjectProperty allows asserting that an object property expression is irreflexive - that is the property does not hold for any individual. Normative Syntax Direct Semantics RDF-Based_Semantics

The OWL 2 construct AsymmetricObjectProperty allows asserting that an object property expression is asymmetric - that is if the property expression OPE holds between the individuals x and y, then it cannot hold between y and x. Normative Syntax Direct Semantics RDF-Based_Semantics

These constructs are part of SROIQ and have been implemented in SROIQ reasoners, or can be easily added to SROIQ.

Use Case #5 Use Case #6 Use Case #8

Note: Many use cases illustrate the desirability for Reflexivity, Irreflexivity, Asymmetry or Local Relexivity. The usefulness of these features was explicitly mentioned by the Health Care and Life Sciences interest group in their last call comment. The Semantic Web Deployment Working Group (SWD) also explicitly mentioned the potential usefulness of reflexivity and asymmetry e.g., for specifying application-specific specializations of SKOS semantic relations (see comment from the SWD). For example, in mereology, the partOf relation is defined to be transitive, reflexive, and antisymmetric. Many applications, which describe complex structures, in life science or systems engineering, require extensive use of part-whole relations, axiomatized in that way. Other relations encountered in ontology modeling require such axiomatizations as well, possibly with different characteristics (e.g., [OBO] [RO]). Examples include proper part of and locative relations (typically transitive and irreflexive), causal relations (typically transitive and irreflexive) and membership relations (typically irreflexive). Another example is the skos:broader relationship. SKOS specification [SKOS] makes no statements regarding the reflexivity or irreflexivity of skos:broader to allow both interpretations: for example it should be considered reflexive for a direct translation of an inferred OWL subclass hierarchy, but irreflexive for most thesauri or classification schemes. OWL 2 reflexivity/irreflexivity allows to add one of these two features on demand. Self restrictions are even more fine grained, allowing to state that skos:broader should only be locally reflexive or irreflexive w.r.t. skos:Concept (via a SubClassOf axiom ) .

2.2.4 F7: Disjoint Properties

While OWL 1 provides means to state the disjointness of classes, it is impossible to state that properties are disjoint.

The OWL 2 construct DisjointObjectProperties allows asserting that several object properties are pairwise incompatible (exclusive); that is, two individuals cannot be connected by both two different properties of the set. This construct is part of SROIQ and has been implemented in SROIQ reasoners. Normative Syntax Direct Semantics RDF-Based Semantics

DisjointDataProperties allows asserting that several data properties are pairwise incompatible (exclusive). Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #1 Use Case #2 Use Case #3

2.2.5 F8: Property Chain Inclusion

OWL 1 does not provide means to define properties as a composition of other properties, like uncle could be defined, hence, it is not possible to propagate a property (e.g.; is:locatedIn) along another property (e.g.; partOf). The OWL 2 construct ObjectPropertyChain in a SubObjectPropertyOf axiom allows defining a property as the composition of several properties. Such axioms are known as complex role inclusions in SROIQ, and if they meet certain regularity conditions have been implemented in SROIQ reasoners. Normative Syntax Direct Semantics RDF-Based Semantics

An axiom SubObjectPropertyOf ( ObjectPropertyChain( OPE₁ ... OPE_n ) OPE) states that any individual x connected with an individual y by a chain of object properties expressions OPE₁, ..., OPE_n is necessary connected with y by the object property OPE.

Use Case #1 Use Case #5 Use Case #7 Use Case #8

2.2.6 F9: Keys

OWL 1 does not provide means to define keys. However, keys are clearly of vital importance to many applications in order to uniquely identify individuals of a given class by values of (a set of) key properties. The OWL 2 construct HasKey allows defining keys for a given class. While in OWL 2 key properties are not required to be functional or total properties, it is always possible to separately state that a key property is functional, if desired. Keys in OWL 2 are a form of DL Safe rule [DL-Safe]. They have been implemented in KAON2 and can be added to other reasoners.

An HasKey axiom states that each named instance of a class is uniquely identified by a (data or object) property or a set of properties - that is, if two named instances of the class coincide on values for each of key properties, then these two individuals are the same. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #2 Use Case #7 Use Case #9

2.3.1 F10: Extra Datatypes and Datatype Restrictions

OWL 1 provides support for only integers and strings as datatypes and does not support any subsets of these datatypes. For example, one could state that every person has an age which is an integer but not to restrain the range of that datatype to say that adults have an age greater than 18. OWL 2 provides new capabilities for datatypes, supporting a richer set of datatypes and restrictions of datatypes by facets, as in XML Schema.

• Extra datatypes

OWL 2 datatypes include a) various kinds of numbers, adding support for a wider range of XML Schema Datatypes (double, float, decimal, positiveInteger, etc.) and providing its own datatypes, e.g., owl:real; b) strings with (or without) a Language Tag (using the rdf:PlainLiteral datatype); and c) boolean values, binary data, IRIs, time instants, etc.

• Datatype Restrictions

DatatypeRestriction makes it also possible to specify restrictions on datatypes by means of constraining facets that constrain the range of values allowed for a given datataype, by length (for strings) e.g. minLength, maxLength, and minimum/maximum value, e.g. minInclusive, maxInclusive. Extended datatypes are allowed in many description logics and are supported by several reasoners. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #9 Use Case #11 Use Case #12 Use Case #18 Use Case #19

In OWL 1 it is not possible to represent relationships between values for one object, e.g., a square is a rectangle whose length equals its width. N-ary datatype support was not added to OWL 2 because there were issues on just what support should be added. However, OWL 2 includes syntactic constructs needed for n-ary datatypes, to provide a common basis for extensions. The Data Range Extension: Linear Equations Note proposes an extension to OWL 2 for defining data ranges in terms of linear (in)equations with rational coefficients.

Use Case #10 Use Case #11

2.3.3 Datatype Definitions

OWL 1 allows to define a new class by a class description but it does not offer means to explicitely define a new datatype. For ease of writing, reading, maintaining ontologies, OWL 2 provides a new construct to define datatypes that occur a couple of times in an ontology (like adult age, legal driving age etc.) .

DatatypeDefinition allows to explicitely name a new datatype. Normative Syntax Direct Semantics RDF-Based Semantics

Use Case #9

2.3.4 Data Range Combinations

While OWL 1 allows to construct a new class by combining classes, it does not provide means to construct a new datatype by combining other ones. In OWL 2 it is possible to define new datatypes by combination of datatypes.

In OWL 2, combinations of data ranges can be constructed using intersection (DataIntersectionOf), union ( DataUnionOf), and complement (DataComplementOf) of data ranges.

Use Case #9

Use Case #12 Use Case #13 Use Case #14 Use Case #15

2.5.1 F13: Annotations

• Annotations on ontology entities and anonymous individuals

OWL 2 provides the construct AnnotationAssertion for annotations of ontology entities (such as classes or properties) and anonymous individuals. These annotations carry no semantics in the OWL 2 Direct Semantics, allowing the direct use of DL reasoners.

• Annotations on Axioms, Annotations, Ontologies

OWL 2 provides the construct Annotation for annotations of axioms and ontologies. It can also be used for annotations of annotations themselves. These annotations carry no semantics in the OWL 2 Direct Semantics, allowing the direct use of DL reasoners.

Use Case #2 Use Case #5 Use Case #12 Use Case #19

• Subproperty of Annotation Property

• Domain of Annotation Property

• Range of Annotation Property

Use Case #2 Use Case #5

2.6.1 F14: Declarations

In OWL 1, an entity such as a class or an object property could be used in an ontology without any prior announcement, so there was no way of ensuring that entity names matched in different axioms. In practice, if an entity name was mistyped in an axiom, there was no way of catching the error. In OWL 2 a declaration signals that an entity is part of the vocabulary of an ontology. A declaration also associates an entity category (class, datatype, object property, data property, annotation property, or individual) to the declared entity. Declarations are not always necessary (see Syntax). Declarations do not affect the meaning of OWL 2 ontologies and thus do not have an effect on reasoning. Implementations may choose to check that every name is declared if desired.

Use Case #17 Use Case #5

2.6.2 Top and Bottom Properties

While OWL 1 had only top and bottom predefined entities for classes, the two classes owl:Thing and owl:Nothing, OWL 2 provides in addition top and bottom object and data properties, namely owl:topObjectProperty, owl:bottomObjectProperty, owl:topDataProperty, and owl:bottomDataProperty.

• all pairs of individuals are connected by owl:topObjectProperty
• no individuals are connected by owl:bottomObjectProperty.
• all possible individuals are connected with all literals by owl:topDataProperty
• no individual is connected by owl:bottomDataProperty to a literal.

2.6.3 IRIs

Uniform Resource Locators (URIs) were used in OWL 1 to identify classes, ontologies, and other ontology elements. URIs are strings formed using a subset of ASCII. This was quite limiting, particularly with respect to non-English language names as ASCII only included letters from the English alphabet. To support broad international needs, OWL 2 uses Internationalized Resource Identifiers (IRIs) [RFC3987] for identifying ontologies and their elements.

2.6.4 Imports and Versioning

In OWL 1 ontologies can be stored as Semantic Web documents, and ontologies can import other ontologies. OWL 2 makes it clear that this importing is by the location of the ontology document.

OWL 2 also clears up the relationship between an ontology name (IRI) and its location and, in response to several requests, provides a simple versioning mechanism by means of version names (IRIs). Each OWL 2 ontology may have an ontology IRI, which is used to identify the ontology. An OWL 2 ontology may also have a version IRI, which is used to identify a particular version of the ontology.

An OWL 2 ontology is stored at its version IRI and one of the ontologies that have the ontology IRI is stored at the ontology IRI as well. If it does not matter which of the versions is desired then importing can use the ontology IRI, but if a particular version is desired then the version IRI is used.

The ontology is stored at its version IRI V. One of the versions using the ontology IRI O should also be stored at O; this is considered to be the current version of the ontology.

Use Case #9

3.1 F15: OWL 2 EL, OWL 2 QL, OWL 2 RL

OWL 1 defined two major dialects, OWL DL and OWL Full, and one syntactic subset (OWL Lite). However, it turned out that it was not sufficient to address needs later enlightened by OWL ontologies and deployment.

• A number of large ontologies, such as life sciences ontologies, e.g.; the FMA, NCI Thesaurus, SNOMED CT, Gene Ontology or some OBO ontologies, are mainly concerned by language scalability and performance problems in reasoning (see for example [FMA]). Such ontologies often need to represent (rather) complex entities (e.g.; anatomical entities composed of parts connected in complex ways) or to allow the propagation of properties (e.g.; location of diseases from parts to whole). They exhibit a huge number of classes and have a heavy use of classification to manage their terminology. OWL 2 defines a new syntactic subset that trades off some expressiveness in return for computational guarantees: OWL 2 EL.
• Many applications involving classical databases, are concerned by interoperability of the language with databases technologies and tools. While the ontologies are relatively lightweight, they exhibit a crucial needs to query very large sets of individuals. OWL 2 defines a new syntactic subset that allows conjunctive queries to be answered using standard relational database technology and to access the data directly via relational queries (e.g., SQL): OWL2 QL.
• Other applications feel concerned by interoperability of the ontology language with rules and existing rule engines. While the ontologies are relatively lightweight, they need to query large datasets, and it may be useful or necessary to operate directly on data in the form of RDF triples. OWL 2 defines a new syntactic subset to accommodate both OWL 2 applications that can trade the full expressivity of the language for efficiency, and RDF(S) applications that need some added expressivity from OWL 2: OWL2 RL.

OWL 2 defines three different profiles : OWL 2 EL, OWL 2 QL, and OWL 2 RL, sublanguages (syntactic subsets) of OWL 2 with useful computational properties (e.g., reasoning complexity in range of LOGSPACE to PTIME) or implementation possibilities (e.g., fragments implementable using RDBs). They are briefly described below, for an extensive description, see Profile.

• restrictions on constructs: OWL 2 EL supports existential quantification to a class expression or a data range, existential quantification to an individual (ObjectHasValue) or a literal (DataHasValue), self-restriction, enumerations involving a single individual or a single literal, intersection of classes and data ranges. Missing features include universal quantification to a class expression or a data range, cardinality restrictions (min, max and exact), disjunction (ObjectUnionOf, DisjointUnion, and DataUnionOf), class negation and many other features, see the precise list of missing features.
• restrictions on axioms: OWL 2 EL supports most axioms e.g., subClass, equivalentClass, class disjointness, range and domain, object property inclusion (SubObjectPropertyOf), possibly involving property chains, and data property inclusion (SubDataPropertyOf)transitive properties, keys (HasKey) …;
• It should be noted that in addition to syntactical restrictions, OWL 2 EL extends the global restrictions on axioms defined in the structural specification [OWL 2 Specification] with an additional condition (see 2.2.6 Global Restrictions ).

In return, respecting OWL 2 EL restrictions offers computational guarantees while not sacrificing too much expressive power OWL 2 EL is a language for which reasoning, including query answering, is known to be worst-case polynomial. It is related to the theory of [EL++] [EL++ Update]. OWL 2 EL enables efficient implementations , E.g., CEL [CEL] is the first reasoner for the description logic EL+; CEL implements a polynomial-time algorithm.

• restrictions on constructs: features include limited form of existential restrictions, subClass, equivalentClass, disjointness, range and domain, symmetric properties, etc.; Missing features are existential quantification to a class expression or a data range, self-restriction,existential quantification to an individual or a literal, enumeration of individuals and literals, universal quantification to a class expression or a data range, cardinality restrictions (min, max and exact), disjunction (ObjectUnionOf, DisjointUnion, and DataUnionOf, property inclusions (SubObjectPropertyOf involving property chains), functional and inverse-functional properties, transitive properties, reflexive properties, irreflexive properties, asymmetric properties, keys, see the Profile document for details on missing features.
• restrictions on axioms: OWL 2 QL supports the same class axioms as in the structural specification [OWL 2 Specification], except DisjointUnion which is disallowed;

In return, respecting OWL 2 QL restrictions offers several benefits:

• These restrictions enable a tight integration with RDBMSs. This profile his suited for relatively lightweight ontologies with very large number of individuals, and where it is useful or necessary to access the data directly via relational queries (e.g., SQL).
• Reasoners can be implemented on top of standard relational database

OWL 2 QL is a language for which reasoning, including query answering, is known to be worst case logspace (same as DB). OWL 2 QL can be implemented on top of standard relational database: the data can be left in the DBs, and query answering simply uses the ontology to rewrite the queries into equivalent SQL queries against the source DBs.

• restrictions on constructs: most OWL 2 constructs of class expressions are supported, but with restrictions of use to certain syntactic positions (see the syntactic restrictions on Class Expressions shown in Table 2). For example, in OWL 2 RL existential quantification to a class, which often occurs in Life Sciences ontologies (e.g., SNOMED) or union of class expressions (ObjectUnionOf) are not allowed on the right hand side of axioms. Standard semantics only apply when they are used in that restricted way;
• restrictions on axioms: OWL 2 RL supports all axioms of OWL 2, except disjoint unions of classes, reflexive object property axioms, and negative object and data property assertions.

In return, respecting OWL 2 RL restrictions offers several benefits:

• These restrictions prevent from infering the existence of non named individuals which makes it possible to implement reasoners using rule-based inference engines, while still providing desirable computational guarantees.
• Reasoners can be implemented on top of rule extended DBMS e.g., SQL (see Implementation Perspective).
• A rule-based implementation can operate directly on RDF triples and so can be applied to an arbitrary RDF graph, i.e., to any OWL 2 ontology. In this case, only correct answers to queries will be computed (reasoning will be sound), but it is not guaranteed to obtain all correct answers (it may not be complete).

OWL 2 RL allows for polynomial reasoning (consistency, classification, and instance checking) using rule-based technologies. It is related to the theory of DLP [DLP] and pD* [pD*]. OWL 2 RL can be implemented on top of rule extended DBMS, using rule-extended database technologies operating directly on RDF triples, E.g., Oracle’s OWL Prime implemented using forward chaining rules applied to triples of the RDF serialization in Oracle 11g (see ORACLE 11gR1 OWL Prime.) [OWL Prime].

Use Case #2 Use Case #3 Use Case #4 Use Case #8 Use Case #16

There are various syntaxes available to serialize and exchange OWL 2 ontologies. The primary exchange syntax for OWL 2 is the RDF/XML Syntax [RDF/XML] which is the only syntax that MUST be supported by implementations. As explained below, the Functional Syntax main purpose is to specify the structure of the language. OWL/XML is an XML serialization motivated by the desire of better interoperability.

• In OWL 1, the abstract syntax (see Section 2 of the OWL 1 Semantics [OWL 1 Semantics]) played the role of both the structure and the functional syntax in OWL 2 [OWL 2 Structural Specification]. The OWL 2 functional syntax differs in form from the OWL 1 abstract syntax, but its role within the overall structure of OWL is identical: it specifies the structure of the language. The OWL 2 functional syntax is much closer to the RDF graph representation and can capture more RDF graphs; it also has a direct correspondence to the structural specification in UML [UML].
• Like OWL 1, OWL 2 specifies a precise mapping from ontology structures (represented using the abstract/functional syntax) to RDF graphs. OWL 2, however, also benefits from an explicitly specified mapping from RDF graphs back to ontology structures [OWL 2 RDF Mapping].
• The two semantics (Direct [OWL 2 Direct Semantics] and RDF-Based [OWL 2 RDF-Based Semantics]) of OWL 2 have their direct counterparts in OWL 1, under the names Direct Model-Theoretic Semantics and RDF-Compatible Model-Theoretic Semantics respectively [OWL 1 Semantics].
• An XML Presentation Syntax was also available for OWL 1 [OWL 1 XML Syntax] (although not as a Recommendation). On the other hand, the Manchester syntax did not exist for OWL 1.
• OWL 1 defined one sub-language (OWL Lite), where OWL 2 defines three (EL, QL, and RL) [OWL 2 Profiles]. OWL Lite has not been re-specified for OWL 2, but because of backward compatibility, OWL Lite ends up as a sub-language of OWL 2.

The central role of RDF/XML as the only required exchange syntax for OWL 2 tools and the relationships between the Direct and RDF-Based semantics (i.e., the correspondence theorem) have not changed. More importantly, backwards compatibility with OWL 1 is complete, both syntactically and semantically.

• Just as in OWL 1, OWL 2 can handle all RDF graphs. The vocabulary that is given special meaning in OWL 2 includes the special vocabulary of OWL 1. However, the use of owl:DataRange, while still possible, is now deprecated — rdfs:Datatype should be used instead.

• The direct semantics for OWL 2 [OWL 2 Direct Semantics] is almost completely compatible with the direct semantics for OWL 1 [OWL 1 Semantics]. The only difference is that annotations are semantics-free in the direct semantics for OWL 2. It is highly unlikely, however, that users will notice this difference: firstly, the semantics given to annotations in the OWL 1 direct semantics was extremely weak and unlikely to lead to any significant entailments; and secondly, OWL 1 tools using the direct semantics typically treat annotations as though they are semantics-free.

• The RDF-based semantics for OWL 2 [OWL 2 RDF-Based Semantics] is completely compatible with the RDF-based semantics for OWL 1 [OWL 1 Semantics]. Some of the details of this semantics have changed, but the set of inferences are the same.

• The treatment of importing in RDF documents has changed slightly in OWL 2 if the RDF graphs are to be conformant OWL 2 DL ontology documents [OWL 2 Conformance]. In OWL 1, importing happened first, so the entire merged graph was considered as one unit [OWL 1 Semantics]. In OWL 2, the individual documents are considered separately in most cases [OWL 2 Structural Specification]. This means that OWL 1 DL RDF documents that do not have a well-specified ontology header may need to be slightly modified to be conforming OWL 2 DL ontology documents.

[OWL 2 Specification]

OWL 2 Web Ontology Language: Structural Specification and Functional-Style Syntax Boris Motik, Peter F. Patel-Schneider, Bijan Parsia, eds. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-syntax-20090611/. Latest version available at http://www.w3.org/TR/owl2-syntax/.

[OWL 2 Direct Semantics]

OWL 2 Web Ontology Language: Direct Semantics Boris Motik, Peter F. Patel-Schneider, Bernardo Cuenca Grau, eds. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-direct-semantics-20090611/. Latest version available at http://www.w3.org/TR/owl2-direct-semantics/.

[OWL 2 RDF-Based Semantics]

OWL 2 Web Ontology Language: RDF-Based Semantics Michael Schneider, editor. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-rdf-based-semantics-20090611/. Latest version available at http://www.w3.org/TR/owl2-rdf-based-semantics/.

[OWL 2 RDF Mapping]

OWL 2 Web Ontology Language: Mapping to RDF Graphs Peter F. Patel-Schneider, Boris Motik, eds. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-mapping-to-rdf-20090611/. Latest version available at http://www.w3.org/TR/owl2-mapping-to-rdf/.

[OWL 2 Profiles]

OWL 2 Web Ontology Language: Profiles Boris Motik, Bernardo Cuenca Grau, Ian Horrocks, Zhe Wu, Achille Fokoue, Carsten Lutz, eds. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-profiles-20090611/. Latest version available at http://www.w3.org/TR/owl2-profiles/.

[OWL 2 Conformance]

OWL 2 Web Ontology Language: Conformance Michael Smith, Ian Horrocks, Markus Krötzsch, eds. W3C Candidate Recommendation, 11 June 2009, http://www.w3.org/TR/2009/CR-owl2-conformance-20090611/. Latest version available at http://www.w3.org/TR/owl2-conformance/.

[OWL 1 Semantics]

OWL Web Ontology Language: Semantics and Abstract Syntax. Peter F. Patel-Schneider, Patrick Hayes, and Ian Horrocks, eds., W3C Recommendation, 10 February 2004.

[OWL 1 XML Syntax]

OWL Web Ontology Language: XML Presentation Syntax. Masahiro Hori, Jérôme Euzenat and Peter F. Patel-Schneider, eds., W3C Note, 11 June 2003.

[RFC 3987]

RFC 3987: Internationalized Resource Identifiers (IRIs). M. Duerst and M. Suignard. IETF, January 2005, http://www.ietf.org/rfc/rfc3987.txt

[RDF/XML]

RDF/XML Syntax Specification (Revised). Dave Beckett and Brian McBride, eds., W3C Recommendation 10 February 2004.

[OWL Use Cases and Requirements]

OWL Web Ontology Language: Use Cases and Requirements Jeff Heflin, ed. 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/.

[SROIQ]

The Even More Irresistible SROIQ. Ian Horrocks, Oliver Kutz, and Uli Sattler. In Proc. of the 10th Int. Conf. on Principles of Knowledge Representation and Reasoning (KR 2006). AAAI Press, 2006.

[SHOIQ]

A Tableaux Decision Procedure for SHOIQ. Horrocks, I., and Sattler, U. In Proc. of 19th International Joint Conference on Artificial Intelligence (IJCAI 2005) (2005), Morgan Kaufmann, Los Altos.).

[Next Steps]

Next Steps to OWL. B. Cuenca Grau, I. Horrocks, B. Parsia, P. Patel-Schneider, and U. Sattler. In Proc. of OWL: Experiences and Directions, CEUR, 2006.

[Syntax Problem]

Problem with OWL Syntax. Boris Motik and I. Horrocks, OWLED 2006, 2006.

[CEL]

CEL—A Polynomial-time Reasoner for Life Science Ontologies. F. Baader, C. Lutz, and B. Suntisrivaraporn. In U. Furbach and N. Shankar, editors, Proceedings of the 3rd International Joint Conference on Automated Reasoning (IJCAR'06), volume 4130 of Lecture Notes in Artificial Intelligence, pages 287–291. Springer-Verlag, 2006.

[SNOMED EL+]

Replacing SEP-Triplets in SNOMED CT using Tractable Description Logic Operators. B. Suntisrivaraporn, F. Baader, S. Schulz, K. Spackman, AIME 2007

[EL++]

Pushing the EL Envelope. Franz Baader, Sebastian Brandt, and Carsten Lutz. In Proc. of the 19th Joint Int. Conf. on Artificial Intelligence (IJCAI 2005), 2005.

[EL++ Update]

Pushing the EL Envelope Further. Franz Baader, Sebastian Brandt, and Carsten Lutz. In Proc. of the Washington DC workshop on OWL: Experiences and Directions (OWLED08DC), 2008.

[DL-Lite]

Tractable Reasoning and Efficient Query Answering in Description Logics: The DL-Lite Family. Diego Calvanese, Giuseppe de Giacomo, Domenico Lembo, Maurizio Lenzerini, Riccardo Rosati. J. of Automated Reasoning 39(3):385–429, 2007.

[DLP]

Description Logic Programs: Combining Logic Programs with Description Logic. Benjamin N. Grosof, Ian Horrocks, Raphael Volz, and Stefan Decker. in Proc. of the 12th Int. World Wide Web Conference (WWW 2003), Budapest, Hungary, 2003. pp.: 48–57

[pD*]

Completeness, decidability and complexity of entailment for RDF Schema and a semantic extension involving the OWL vocabulary. Herman J. ter Horst. J. of Web Semantics 3(2–3):79–115, 2005.

[OWLPrime]

Implementing an Inference Engine for RDFS/OWL Constructs and User-Defined Rules in Oracle. Zhe Wu Eadon, G. Das, S. Chong, E.I. Kolovski, V. Annamalai, M. Srinivasan, J. Oracle, Nashua, NH; Data Engineering, 2008. ICDE 2008. IEEE 24th International Conference on, pages 1239-1248, Cancun, 2008.

[Metamodeling]

On the Properties of Metamodeling in OWL. Boris Motik. On the Properties of Metamodeling in OWL. Journal of Logic and Computation, 17(4):617–637, 2007.

[Datatype]

OWL Datatypes: Design and Implementation. Boris Motik, Ian Horrocks, ISWC 2008, Karlsruhe, Deutshland, 2008.

[XML Schema]

W3C XML Schema Definition Language (XSD) 1.1 Part 1: Structures. Shudi Gao, C. M. Sperberg-McQueen, and Henry S. Thompson, eds. W3C Candidate Recommendation, 30 April 2009, http://www.w3.org/TR/2009/CR-xmlschema11-1-20090430/. Latest version available as http://www.w3.org/TR/xmlschema11-1/.

[DL-Safe]

Query Answering for OWL-DL with Rules. Boris Motik, Ulrike Sattler and Rudi Studer. Journal of Web Semantics: Science, Services and Agents on the World Wide Web, 3(1):41–60, 2005.

All use cases are presented using the following pattern: Overview, Features, Example for, References. The Overview only gives a general description of the use cases. Features lists several features required by the use case after the paper. Example points to a feature and short example which has been selected to illustrate a specific new feature of OWL 2. This same information can be seen in an abbreviated form in Table 3.2. For an easy access, References points to the related papers available online which URL is provided in the bibliography of the Appendix.

Example for: Disjoint Union

• E.g.; Lobe is a disjoint union of :FrontalLobe :ParietalLob :TemporalLobe :OccipitalLobe and :LimbicLobe.

References: [MEDICAL REQ] [Ontology with rules] [Brain Imaging ]

Example for: Disjoint Classes

• E.g.; Nothing can be both a :LeftLung and a :RightLung.

References: [FMA]

Example for: Qualified Cardinality Restrictions

• E.g.; for specifying the number and types of functional groups.

References: [Chemistry]

Example for: Qualified Cardinality Restrictions

• E.g.; the class of automobile having exactly 2 rear doors.

References: [Auto]

Example for: Asymmetric

• E.g.; if p is a proper part of q then q cannot be a proper part of p.

References: [OBO] [RO] [OBO2OWL]

Example for: Irreflexive

• E.g.; Nothing flows into itself.

References: [Ordnance]

Without property chain inclusion axioms, adoption of OWL by the SNOMED community would have required awkward workarounds with their attendant complications and complexities - effectively killing movement in that direction. With [them], we have a clear path to using OWL 2 for further development and integration with other biomedical ontologies. The required property chain inclusion axioms allow to encode inheritance of properties along another property, e.g., part-of, which is of utmost importance in anatomy. For example, with axioms such as has-location ◦ proper-part-of < has-location injury to finger can be inferred as injury to hand. As reported in [SNOMED EL+] by re-engineering SNOMED-CT in this way, the number of anatomical classes dropped from 54,380 to 18,125, and the time needed by the CEL reasoner [CEL] (version 0.94) from 900.15 seconds to 18.99 seconds.
Like the FMA, given the common use of cross-references between SNOMED and other biomedical ontologies via concepts ID, keys would be highly useful as well.

Features: Property chain inclusion axioms, Keys, Profiles (OWL 2 EL)

Example for: Property chain

• E.g.; anything located in a part is located in the whole

References: [SNOMED REQ]

Example for: Reflexive

• E.g.; a frontal lobe is part of a brain hemisphere or a car is part of a car

Note: according to the definition given in OBO, the whole is being considered as a part [Part Whole] but there are controversial opinions asserting that 'part of' is not reflexixe.

References: [Part Whole]

Example for: NegativePropertyAssertion

• E.g.; This patient is not 5 years old.

References: [Agence Biomedecine] [Transplant Ontology]

Overview: This use case is based on an ongoing W3C task force on Clinical Observations Interoperability where the goal is to enable re-use and sharing of clinical data created in healthcare delivery in the Clinical Trials context. In particular the first application chosen to demonstrate feasibility of the interoperability approach is that of patient recruitment. In this case, a sample set of clinical trial protocols available from http://www.clinicaltrials.gov each of which contains a list of eligibility (inclusion and exclusion criteria). These eligibility criteria are used for identify eligible patients and potentially form conditions in a SPARQL query or could be represented as OWL classes. They also need to be mapped as per the discussion in the use case above. A list of requirements based on an analysis of these clinical trial protocols is available from http://esw.w3.org/topic/HCLS/ClinicalObservationsInteroperability?action=AttachFile&do=get&target=FunctionalRequirements_v1.xls

In particular, one of the clinical trials requires that the enrolment date of a clinical trial participant be within 30 days after the patient has been started on a particular therapy. This motivated the need for N-ary datatypes with inequality expressions.

Features: [N-Ary]

Example for: N-ary Datatypes

• E.g.; the enrolment date of a clinical trial participant should be within 30 days after the patient has been started on a particular therapy

Overview: [N-ary] presents many Use cases that would benefit from various datatype extensions

Features: Datatypes restriction, [N-Ary]

Example for: N-ary Datatypes

• E.g.; datatypes restrictions like intervals, or N-Ary datatype with inequality such as needed in Use Case #10.

References: [N-ary]

Overview: [Protege] reported in 2005 on Protégé experiences with the development of OWL support, and on the experiences of the user community with OWL at that time. While the overall feedback from the community was positive, their experience suggested that there were considerable gaps between the user requirements, the expressivity of OWL, and users’ understanding of OWL. To summarize, based on their experiences, Protégé developers suggested a number of extensions to a future version of OWL namely, Integration of user-defined datatypes (esp. for numeric ranges), Qualified Cardinality Restrictions, Management of disjointness (owl:AllDisjoint), More flexible annotation properties (at least as best practices). This report underlined that one of the omissions in the OWL language that users complain about most often is poor representation of numeric expressions. Almost all groups, except for those developing traditional medical terminologies, sorely need to be able to express quantitative information. Typical examples include the length between 1mm and 2mm, age greater than 18 years, pressure in the range of 1030mb to 1035mb. Such range declarations are needed to classify individuals and to build class definitions such as Adult, and should therefore be supported by reasoners. User base points out that the current OWL datatype formalism is much too weak to support most real world applications and that many potential users therefore cannot adopt OWL. "The user communities anxiously await an extension to the OWL specification to represent user-defined datatypes with XML Schema facets such as xsd:minInclusive." It also points out some limitations related to annotations or metamodeling from an implementors perspective: "Despite the value of annotation properties, in OWL DL, properties that are declared as annotation properties are greatly limited in so far that they can neither have range or domain constraints, nor can they be arranged in sub-property hierarchies. This type of information about a property enables tools to control the values that annotation properties can acquire. Without range constraints it is difficult to provide the user with appropriate input widgets. In a similar sense, it is often helpful to declare meta-classes so that classes can be categorized into types and different interfaces be pro-vided for each type. Currently, using these features means that the ontology will be forced into OWL Full."

Features: Qualified cardinality restriction, Datatypes restriction, Annotations, metamodeling

Example for: Extra Datatypes

• E.g.; adults are individuals whose age is greater than 18 years.

References: [Protege]

Overview: People often want to use a class to specify the value of some property. An example originating at the University of Karlsruhe [Web Service] is in service modeling. Services are modeled as instances of the :Service class. For each concrete service (i.e., for each instance of :Service), the users wanted to state what the input to the service is. Here is an example of a service description:

(1) :Service rdf:type owl:Class
(2) :Person rdf:type owl:Class
(3) s1 rdf:type :Service
(4) s1 :input :Person

s1 is an individual of the class :Service due to (1) and (3), and :Person is a class due to (2); hence, in (4) we have a relationship :input between an individual and a class. Hence, you need some kind of metamodeling to solve this problem. One way would be that the name 'Person' may refer both to Person as a class and as an individual denoting Person as a whole (Class ↔ Individual)

Features: metamodeling

Example for: Simple metamodeling

• E.g.; a class and an individual : Person may be used both for a class and an individual

References: [Web Service] [Punning]

Overview: It can be useful to relate schema elements (classes/properties) with each other in order to capture pragmatic relationships between them. An example observed in applications of Semantic MediaWiki (a simple but widely used OWL-based semantic content management system with light-weight expressiveness) [OWL1.1 Wiki] is that users wish to relate schema elements to indicate domain-specific relationships, and generally to organize ontological vocabulary. Examples are statements such as:

• "The property is_located_in is in the class Deprecated_Properties and was replaced by property has_location."
• "Objects of the class City should have a value for the property population." (expressed by relating class and property)

These are merely pragmatic descriptions, and no logical relationship on schema-level is intended. However, in collaborative vocabulary creation, it is relevant that users can express such intended relationships. An important aspect of Semantic MediaWiki is that users can also query for semantic information, and this is currently realized as intended by punning. Semantic MediaWiki has already been extended by using off-the-shelf OWL reasoners, and it would be desirable if such systems would be able to deal with the use of punning in such simple cases; (Class/Property ↔ Individual)

Features: metamodeling

Example for: Simple metamodeling

• E.g.; a property and an individual: to make a statement asserting that a property is an individual of the class Deprecated_properties

References: [Wiki] [Punning]

Overview: The Unified Modeling Language (UML) includes a modeling element known as an Association Class which combines the features of a UML Class and a UML Association (UML's construct for defining class to class relationships Association). The Association Class, e.g., the association between classes Person and Company allows a modeler to define a relation as an association and reify it simultaneously. This is convenient when one wants to model attributes of relations themselves. One way to support such case might be Class and ObjectProperty punning (Class ↔ ObjectProperty).

Features: metamodeling

Example for: Simple metamodeling

• E.g.; an object property and a class: PersonCompany may be used both for an object property and a class.

References: [UML] [Punning]

Example for: Profiles

• E.g.; OWL 2 QL profile to easily query a federation of databases in a convivial way

References: [Who reads?]

Overview: A user adds an assertion to an ontology; however, he accidentally mistypes the IRI of an individual. It should be possible to detect this error by comparing the IRI of the individual in the axiom with the IRIs explicitly declared to be a part of the ontology: if the individual IRI has not been explicitly introduced as being in the ontology, the user should be given the opportunity to correct his error. Tools developers, such as those involved in the Protégé-OWL toolset architecture [TOOLS], have often expressed problems raised for e.g.; APIs [OWL API] due to lack of declarations. "The first problem is that OWL does not allow for explicit declarations—assertions that a certain class, property, or an individual exists in an ontology. This aspect of the OWL standard was often misinterpreted, which caused design errors in OWL APIs" [Syntax Problem].

Features: Declaration

Example for: Declaration

• E.g.; A person is declared to be a class of an ontology.

References: [Syntax Problem]

Overview: Numerous single discipline and multi-discipline virtual observatories (e.g., http://vsto.org , http://vmo.nasa.gov/ ) are beginning to use semantic technologies to provide data access and integration. A virtual observatory is a suite of software applications on a set of computers that allows users to uniformly find, access, and use resources (data, software, document, and image products and services using these) from a collection of distributed product repositories and service providers. A VO is a service that unites services and / or multiple repositories. from http://lwsde.gsfc.nasa.gov/VO_Framework_7_Jan_05.doc. Some Virtual Observatories are focusing quite heavily on provenance encoding at data ingest time (e.g., http://spcdis.hao.ucar.edu/ ). The Virtual Solar Terrestrial Observatory (VSTO) is a National Science Foundation and National Center for Atmospheric Research supported effort that allows researchers to find solar and solar-terrestrial data. It provides an ontology-enhanced interface to semantically-enhanced web services that help access a number of online repositories of scientific data. The background OWL ontology contains term descriptions for science terms including instruments, observatories, parameters, etc. Users essentially need to specify a description of the data they wish to retrieve which includes either a specific instrument class or a description of that class, a date range for the data taken, and the parameters. In order to specify that in relevant science terms, scientists need to be able to represent numerical ranges and comparisons going beyond the numeric support of OWL 1. The application also needs to expand to include spatial descriptions. It would use representational power if provided for spatial/geographic containment.

Requirements: Qualified Cardinality, Datatype restriction, [Defaults]

Example for: Datatype restriction

• E.g.; the range for atmosphere is above 18000 and below 19600 [feet]

References: [VSTO]

Example for: Extended annotation to attach annotations

• E.g.; comments on axioms, such as a SubClass axiom, to express for instance that the the elements of the subclass are data generated by a log parser.

References: [NCAR]

Example for: Local reflexivity

• E.g.; An Auto-Phosphorylating Kinase (is a kinase that) :phosphorylates itself.

References: [BIO]

[Medical Req]

Web ontology language requirements w.r.t expressiveness of taxonomy and axioms in medicine In Proc. of ISWC 2003

[Micro Theory]

Creation and Usage of a "Micro Theory" for Long Bone Fractures: An Experience ReportHoward Goldberg, Vipul Kashyap and Kent Spackman, In Proc. of KR-MED 2008..

[Ontology with Rules]

Ontology enriched by rules for identifying brain anatomical structures In RIF 2004, Washington, 2004. and Annex.

[Brain Imaging]

Towards an Hybrid System Using an Ontology Enriched by Rules for the Semantic Annotation of Brain MRI Images In Proc. of RR 2007

The Brain Anatomy Case Study In Proc. of Protege 2005.

[FMA]

The Foundational Model of Anatomy A

The Foundational Model of Anatomy B

The Foundational Model of Anatomy C.

[Chemistry]

Describing chemical functional groups in OWL-DL for the classification of chemical compounds Natalia Villanueva-Rosales and Michel Dumontier. In OWL: Experiences and Directions (OWLED 07), Innsbruck, Austria.

Modelling Life Sciences knowledge with OWL1.1 (OWLED 08 DC)

[Auto]

An exploratory study in an automotive company.

[OBO]

The OBO Foundry: coordinated evolution of ontologies to support biomedical data integration. Barry Smith et al. .

[RO]

Relations in Biomedical Ontologies. .

[OBO2OWL]

OBO to OWL: Go to OWL1.1! (OWLED 07)

OBO and OWL: Leveraging Semantic Web Technologies for the Life Sciences In Proc. of ISWC 2007.

[Ordnance]

Experiences of using OWL at the Ordnance Survey.

[SNOMED REQ]

An examination of OWL and the requirements of a large health care terminology.

[Agence Biomedecine]

Changing Kidney Allocation Policy in France: the Value of Simulation.

[Transplant Ontology]

Construction of the dialysis and transplantation ontology.

[Little Web]

A little semantic web goes a long way in biology Wolstencroft, K., Brass, A., Horrocks, I., Lord, P., Sattler, U., Stevens, R., Turi, D. In Proceedings of the 2005 International Semantic Web Conference (ISWC 2005), pp. 786-800. Springer, Berlin Heidelberg New York (2005).

[Part Whole]

Simple part-whole relations in OWL Ontologies Alan Rector, Chris Welty. W3C Editor's Draft 11 Aug 2005 .

[TOOLS]

Supporting Early Adoption of OWL 1.1 with Protege-OWL and FaCT++. Matthew Horridge and Dmitry Tsarkov and Timothy Redmond. In OWL: Experiences and Directions (OWLED 06), Athens, Georgia.

[OWL API]

Igniting the OWL 1.1 Touch Paper: The OWL API Matthew Horridge and Sean Bechhofer and Olaf Noppens (2007). In OWL: Experiences and Directions (OWLED 07), Innsbruck, Austria.

[Protege OWL]

The Protégé OWL Experience Holger Knublauch, Matthew Horridge, Mark Musen, Alan Rector, Robert Stevens, Nick Drummond, Phil Lord, Natalya F. Noy2, Julian Seidenberg, Hai Wang. In OWL: Experiences and Directions (OWLED 05), Galway, Ireland, 2005.

[N-ary]

N-ary Data predicate use case.

[Web Service]

Preference-based Selection of Highly Configurable Web Services Steffen Lamparter, Anupriya Ankolekar, Stephan Grimm, Rudi Studer: WWW-07, Banff, Canada, 2007.

[Wiki]

Reusing Ontological Background Knowledge in Semantic Wikis Denny Vrandecic, Markus Krötzsch, Proceedings 1st Workshop on Semantic Wikis. Budva, Montenegro, June 2006 .

[UML]

Association.

[Punning]

Punning Use Cases.

[Who reads?]

Who reads our documents?

NIF

NIF Data-Integration slides

[VSTO]

The Virtual Solar-Terrestrial Observatory: A Deployed Semantic Web Application Case Study for Scientific Research McGuinness, D.L., Fox, P., Cinquini, L., West, P., Garcia, J., Benedict, J.L., Middleton, D..

VSTO2.

VMO.

[NCAR]

Semantic Provenance Capture in Data Ingest Systems .

[BIO]

Springer.

pnas.

[SKOS]

W3C Working Draft 29 August 2008 .

The starting point for the development of OWL 2 was the OWL1.1 member submission, itself a result of user and developer feedback, and in particular of information gathered during the OWL Experiences and Directions (OWLED) Workshop series. The working group also considered postponed issues from the WebOnt Working Group.

This document has been produced by the OWL Working Group (see below), and its contents reflect extensive discussions within the Working Group as a whole. The editors extend special thanks to Elisa Kendall (Sandpiper Software), Peter F. Patel-Schneider (Bell Labs Research, Alcatel-Lucent) and Alan Ruttenberg (Science Commons) for their thorough reviews.

The regular attendees at meetings of the OWL Working Group at the time of publication of this document were: Jie Bao (RPI), Diego Calvanese (Free University of Bozen-Bolzano), Bernardo Cuenca Grau (Oxford University), Martin Dzbor (Open University), Achille Fokoue (IBM Corporation), Christine Golbreich (Université de Versailles St-Quentin and LIRMM), Sandro Hawke (W3C/MIT), Ivan Herman (W3C/ERCIM), Rinke Hoekstra (University of Amsterdam), Ian Horrocks (Oxford University), Elisa Kendall (Sandpiper Software), Markus Krötzsch (FZI), Carsten Lutz (Universität Bremen), Deborah L. McGuinness (RPI), Boris Motik (Oxford University), Jeff Pan (University of Aberdeen), Bijan Parsia (University of Manchester), Peter F. Patel-Schneider (Bell Labs Research, Alcatel-Lucent), Sebastian Rudolph (FZI), Alan Ruttenberg (Science Commons), Uli Sattler (University of Manchester), Michael Schneider (FZI), Mike Smith (Clark & Parsia), Evan Wallace (NIST), Zhe Wu (Oracle Corporation), and Antoine Zimmermann (DERI Galway). We would also like to thank past members of the working group: Jeremy Carroll, Jim Hendler, Vipul Kashyap.