Table of Contents. iii

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Jemimah Ward
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2 Current Web Current Web History Current Web Characteristics Current Web Features Current Web Benefits Current Web Applications Why the Current Web is not Enough v Information Must be Structured Finding Requires Metadata Semantics Must be Explicit Current Web Summary 6 Semantic Web Introduction Web Information Representation Challenges Increased Need for Information Representation Ambiguous Human Descriptions Software Demands for Specificity Requirements for a Web Information Representation Solution Minimizing Human Investment Satisfying Computer Requirements Compromise Semantic Web to the Rescue Semantic Web History Semantic Web Vision Populating the Semantic Web Use Cases Appropriate Applications Semantic Web Introduction Summary 23 Ontologies - Enablers of the Semantic Web Ontology Definitions Computer Science Definition Types of Ontologies Gruber Definition OWL-Specific Ontology Definitions Ontology Features Common Understanding of a Domain Explicit Semantics Expressiveness...30 i

3 3.2.4 Sharing Information Ontology Development Issues Describing Semantics Information Representation Building Blocks Relating Information Representation Constructs Semantic Relationships within Building Blocks Semantics Summary Ontology Languages Frame-Based Systems Description Logics Ontologies Summary 42 4 OWL Introduction OWL Features Semantic Web's Layered Architecture Technology Support for the Layers OWL Introduction Summary 46 5 URIs and Namespaces Absolute URIs URI References XML Namespaces (xmlns) Specifying an Alternative Base URI (xml:base) URIs and Namespace Summary 60 6 XML XML Overview XML Features Syntax and Structure XML Declaration Elements XML Element Attributes XML Schema Datatypes User Defined Datatypes Built-in OWL Datatypes : XML Summary, Why XML is not Enough 73 7 RDF RDF Overview Metadata RDF Purpose RDF Specification 77 ii

4 7.2 RDF Features RDF Data Model Resources Literals Statements RDF Summary Why RDF is not Enough 82 8 RDF/XML RDF/XML Overview ~ Relation to XML RDF/XML Specifications RDF Syntax Features (Using XML) RDF/XML Documents File Header (rdf:rdf) Resource Names RDF/XML Statements (rdf:description) Describing the Subject of an RDF Statement Describing a Statement's Property Describing a Statement Value Compound Property Values Striped Syntax RDF Description Summary RDF/XML Summary Why RDF/XML is not Enough RDFS Ill 9.1 RDFS Overview Ill 9.2 RDFS Features RDFS Classes RDFS Class Concept Predefined RDFS Classes Individuals Properties, Vocabulary for RDF Core Properties RDFS Clarification Properties RDFS Container Classes and Properties RDFS Documentation Properties RDFS Summary Why RDFS is not Enough OWL Language 133 iii

5 10.1 OWL Overview OWL Definition OWL History OWL Specification OWL Features OWL Species OWL Full OWLDL OWL Lite OWL Species Summary t OWL Language Summary Encoding an OWL Ontology OWL Ontology File Structure OWL Header XML Declaration and RDF Start Tag Namespaces for OWL Ontology Files Ontology Element (owl.ontology) OWL Header Summary Body Footer - Closing Tag OWL Encoding Summary Defining Basic OWL Lite Classes and Properties Defining a Simple Named Class (owl:class) Predefined OWL Classes (Extreme Classes) Thing Class (owl:thing) Nothing Class (owl:nothing) Describing OWL Lite Properties Datatype Properties (owl:datatypeproperty) Object Properties (owl:objectproperty) Annotation Properties (owl:annotationproperty) Ontology properties (owl:ontologyproperty) Basic OWL Lite Classes and Properties Summary > Describing OWL Lite Property Characteristics Defining Global Property Restrictions Functional Property (owl:functionalproperty) Inverse Functional Property (owl:inversefunctionalproperty) Relating Properties Stating Property Equivalence (owbequivalentproperty) Identifying Inverse Properties (owl:inverseof Property) 179 iv

6 13.3 Inference Shortcuts Transitive Properties (owl:transitiveproperty) Symmetric Properties (owlsymmetricproperty) Local Property Restrictions (owl:restriction/owl:onproperty) Value Constraints OWL Lite Restricted Cardinality OWL Lite Property Characteristics Summary Deriving OWL Lite Classes Simple Named Subclass (rdfs:subclassof) Class Equivalency (owl:equivalentclass) OWL Lite Intersection (owhintersectionof) Derived OWL Lite Classes Summary Describing Individuals Determining an Individual Individual vs. Instance Class vs. Individual Leaves of a Taxonomy Encoding an Instance File Instantiating Individuals Naming Individuals Joining a Class Describing an Individual Associating Property Values at Instantiation Describing Existing Individuals Automating Descriptions of Individuals Relating Individuals Equivalent Individuals (owl:sameas) Differentiating Individuals (owl:differentfrom) Differentiating Groups of Individuals (owl:alldifferent/owl:distinctmembers) Describing Individuals Summary OWL Lite Summary OWL Lite Constructs OWL Lite Restrictions OWLDL..., OWL DL Restrictions OWL DL Vocabulary Complex Classes / Class Expressions Enumerated Classes (owl:oneof) 225 v

7 Disjoint Classes (owl:disjointwith) Boolean Class Combinations Requiring a Property Value (owl:hasvalue) Enumerated Data Values (owl:datarange) OWL DL Summary OWL Full OWL Full's Differing Perspective/Relaxation Type Separation Individuals Classes as Individuals Properties Property Restrictions OWL Full Summary OWL Dialect Selection Choosing Your Weapon Migrating XML and RDF Implementations to OWL Language Selection Summary Satisfaction of Information Representation Requirements OWL Dialect Selection Summary Applications Application Example OWL Lite Solution Supporting Applications Inappropriate Applications Appropriate Applications Applications Summary 259 VI

Short notes about OWL 1

University of Rome Tor Vergata Short notes about OWL 1 Manuel Fiorelli fiorelli@info.uniroma2.it [1] this presentation is limited to OWL 1 features. A new version of OWL (OWL 2), which adds further features