Chapter 7 Ontology Engineering Grigoris Antoniou Frank van Harmelen 1 Chapter 7 A Semantic Web Primer
1 Chapter 7 A Semantic Web Primer Chapter 7 Ontology Engineering Grigoris Antoniou Frank van Harmelen
Lecture Outline Introduction 2. Constructing Ontologies Manually 3. Reusing Existing Ontologies 4. Using Semiautomatic Methods 5. On-To-Knowledge SW architecture Chapter 7 A Semantic Web primer
2 Chapter 7 A Semantic Web Primer Lecture Outline 1. Introduction 2. Constructing Ontologies Manually 3. Reusing Existing Ontologies 4. Using Semiautomatic Methods 5. On-To-Knowledge SW Architecture
Methodological Questions How can tools and techniques best be applied? Which languages and tools should be used in which circumstances. and in which order What about issues of quality control and resource management? Many of these questions for the semantic Web have been studied in other contexts E.g. software engineering, object-oriented design and knowledge engineering 3 Chapter 7 A Semantic Web primer
3 Chapter 7 A Semantic Web Primer Methodological Questions – How can tools and techniques best be applied? – Which languages and tools should be used in which circumstances, and in which order? – What about issues of quality control and resource management? ⚫ Many of these questions for the Semantic Web have been studied in other contexts – E.g. software engineering, object-oriented design, and knowledge engineering
Lecture Outline Introduction 2. Constructing Ontologies Manually 3. Reusing Existing Ontologies 4. Using Semiautomatic Methods 5. On-To-Knowledge SW architecture Chapter 7 A Semantic Web primer
4 Chapter 7 A Semantic Web Primer Lecture Outline 1. Introduction 2. Constructing Ontologies Manually 3. Reusing Existing Ontologies 4. Using Semiautomatic Methods 5. On-To-Knowledge SW Architecture
Main Stages in Ontology Development 1. Determine scope 2. Consider reuse 3. Enumerate terms 4. Define taxonomy 5. Define properties 6. Define facets 7. Define instances 8. Check for anomalies Not a linear process 5 Chapter 7 A Semantic Web primer
5 Chapter 7 A Semantic Web Primer Main Stages in Ontology Development 1. Determine scope 2. Consider reuse 3. Enumerate terms 4. Define taxonomy 5. Define properties 6. Define facets 7. Define instances 8. Check for anomalies Not a linear process!
Determine Scope o There is no correct ontology of a specific domain An ontology is an abstraction of a particular domain and there are always viable alternatives e What is included in this abstraction should be determined b the use to which the ontology will be put by future extensions that are already anticipated 6 Chapter 7 A Semantic Web primer
6 Chapter 7 A Semantic Web Primer Determine Scope ⚫ There is no correct ontology of a specific domain – An ontology is an abstraction of a particular domain, and there are always viable alternatives ⚫ What is included in this abstraction should be determined by – the use to which the ontology will be put – by future extensions that are already anticipated
Determine Scope(2 Basic questions to be answered at this stage are What is the domain that the ontology will cover? For what we are going to use the ontology? For what types of questions should the ontology provide answers? Who will use and maintain the ontology? 7 Chapter 7 A Semantic Web primer
7 Chapter 7 A Semantic Web Primer Determine Scope (2) ⚫ Basic questions to be answered at this stage are: – What is the domain that the ontology will cover? – For what we are going to use the ontology? – For what types of questions should the ontology provide answers? – Who will use and maintain the ontology?
Consider reuse o With the spreading deployment of the Semantic Web, ontologies will become more widely available o We rarely have to start from scratch when defining an ontology There is almost always an ontology available from a third party that provides at least a useful starting point for our own ontology 8 Chapter 7 A Semantic Web primer
8 Chapter 7 A Semantic Web Primer Consider Reuse ⚫ With the spreading deployment of the Semantic Web, ontologies will become more widely available ⚫ We rarely have to start from scratch when defining an ontology – There is almost always an ontology available from a third party that provides at least a useful starting point for our own ontology
Enumerate Terms e Write down in an unstructured list all the relevant terms that are expected to appear in the ontology Nouns form the basis for class names Verbs(or verb phrases) form the basis for property names o Traditional knowledge engineering tools(e. g laddering and grid analysis) can be used to obtain the set of terms an initial structure for these terms 9 Chapter 7 A Semantic Web primer
9 Chapter 7 A Semantic Web Primer Enumerate Terms ⚫ Write down in an unstructured list all the relevant terms that are expected to appear in the ontology – Nouns form the basis for class names – Verbs (or verb phrases) form the basis for property names ⚫ Traditional knowledge engineering tools (e.g. laddering and grid analysis) can be used to obtain – the set of terms – an initial structure for these terms
Define Taxonomy o Relevant terms must be organized in a taxonomic hierarchy Opinions differ on whether it is more efficient/reliable to do this in a top-down or a bottom-up fashion Ensure that hierarchy is indeed a taxonomy If A is a subclass of B, then every instance of A must also be an instance of B(compatible with semantics of rdfs sub classof 10 Chapter 7 A Semantic Web primer
10 Chapter 7 A Semantic Web Primer Define Taxonomy ⚫ Relevant terms must be organized in a taxonomic hierarchy – Opinions differ on whether it is more efficient/reliable to do this in a top-down or a bottom-up fashion ⚫ Ensure that hierarchy is indeed a taxonomy: – If A is a subclass of B, then every instance of A must also be an instance of B (compatible with semantics of rdfs:subClassOf