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Pal gov.tutorial4.session8 2.stepwisemethodologies Pal gov.tutorial4.session8 2.stepwisemethodologies Presentation Transcript

  • ‫أكاديمية الحكومة اإللكترونية الفلسطينية‬ The Palestinian eGovernment Academy www.egovacademy.psTutorial 4: Ontology Engineering & Lexical Semantics Session 8.2 Stepwise Methodologies Dr. Mustafa Jarrar University of Birzeit mjarrar@birzeit.edu www.jarrar.info PalGov © 2011 1
  • AboutThis tutorial is part of the PalGov project, funded by the TEMPUS IV program of theCommission of the European Communities, grant agreement 511159-TEMPUS-1-2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.psProject Consortium: Birzeit University, Palestine University of Trento, Italy (Coordinator ) Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium Palestine Technical University, Palestine Université de Savoie, France Ministry of Telecom and IT, Palestine University of Namur, Belgium Ministry of Interior, Palestine TrueTrust, UK Ministry of Local Government, PalestineCoordinator:Dr. Mustafa JarrarBirzeit University, P.O.Box 14- Birzeit, PalestineTelfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011 2
  • © Copyright NotesEveryone is encouraged to use this material, or part of it, but shouldproperly cite the project (logo and website), and the author of that part.No part of this tutorial may be reproduced or modified in any form or byany means, without prior written permission from the project, who havethe full copyrights on the material. Attribution-NonCommercial-ShareAlike CC-BY-NC-SAThis license lets others remix, tweak, and build upon your work non-commercially, as long as they credit you and license their new creationsunder the identical terms. PalGov © 2011 3
  • Tutorial Map Topic Time Session 1_1: The Need for Sharing Semantics 1.5 Session 1_2: What is an ontology 1.5 Intended Learning ObjectivesA: Knowledge and Understanding Session 2: Lab- Build a Population Ontology 3 4a1: Demonstrate knowledge of what is an ontology, Session 3: Lab- Build a BankCustomer Ontology 3 how it is built, and what it is used for. Session 4: Lab- Build a BankCustomer Ontology 3 4a2: Demonstrate knowledge of ontology engineering and evaluation. Session 5: Lab- Ontology Tools 3 4a3: Describe the difference between an ontology and a Session 6_1: Ontology Engineering Challenges 1.5 schema, and an ontology and a dictionary. Session 6_2: Ontology Double Articulation 1.5 4a4: Explain the concept of language ontologies, lexical semantics and multilingualism. Session 7: Lab - Build a Legal-Person Ontology 3B: Intellectual Skills Session 8_1: Ontology Modeling Challenges 1.5 4b1: Develop quality ontologies. Session 8_2: Stepwise Methodologies 1.5 4b2: Tackle ontology engineering challenges. 4b3: Develop multilingual ontologies. Session 9: Lab - Build a Legal-Person Ontology 3 4b4: Formulate quality glosses. Session 10: Zinnar – The Palestinian eGovernment 3C: Professional and Practical Skills Interoperability Framework 4c1: Use ontology tools. Session 11: Lab- Using Zinnar in web services 3 4c2: (Re)use existing Language ontologies. Session 12_1: Lexical Semantics and Multilingually 1.5D: General and Transferable Skills d1: Working with team. Session 12_2: WordNets 1.5 d2: Presenting and defending ideas. Session 13: ArabicOntology 3 d3: Use of creativity and innovation in problem solving. Session 14: Lab-Using Linguistic Ontologies 3 d4: Develop communication skills and logical reasoning abilities. Session 15: Lab-Using Linguistic Ontologies 3 PalGov © 2011 4
  • Outline and Session ILOsThis session will help student to:4a1: Demonstrate knowledge of what is an ontology, how it is built, and what it is used for.4b1: Develop quality ontologies. PalGov © 2011 5
  • MethodologyWhat are the phases of the ontology development lifecycle? taking into account that Ontologies might be builtcollaboratively by many people.Let’s discuss from where to start, if you want to build anontology for: • E-government • E-Banking • E-Health • Bioinformatics • Multilingual search engine • … PalGov © 2011 6
  • Methodological Questions – Which tools and techniques to use? – Which languages should be used in which circumstances, and in which order? – What quality measures should we care about? – What things can be reused? – Which people should be assigned which tasks? – ....• Many Methodologies exist ! But non is good! Because each project/application/domain is different, and the background of the people involved are also different, etc.• We will overview some common steps in this lecture, thus try to learn smartly, and don’t follow these steps literally. You should have your own methodology for each ontology. PalGov © 2011 7
  • Most methodologies propose these phases:1- Identify Purpose and Scope2- Building the Ontology 2.1- Ontology Capture 2.2- Ontology Coding3- Integrating existing ontologies4- Evaluation5- Documentation PalGov © 2011 8
  • 1- Purpose and Scope• There is no one/ideal ontology of a certain domain – There are always alternatives, each abstracting different things, and for different usages.• What should be included in the ontology (concepts and relations) should be smartly determined, taking into account (if possible) many application scenarios. – Interoperability between systems. – improve search quality. – Communication between people and organizations (important). … – Future extensions should be anticipated. PalGov © 2011 9
  • 1- Purpose and Scope• When you specify the purpose and scope, you should specify the following: 1- What is the domain that the ontology will cover? The notion of context, in the double articulation theory, is part of the Purpose and Scope. That is: the scope where the vocabulary interpretation should be valid. For example: the scope of the legal-Person ontology is the set of all laws, regulations, and repositories in the state. 2- What we are going to use the ontology for?  Enough description about what application scenarios are taking into account. Be carful with the ontology usability/reusability trade-off PalGov © 2011 10
  • 2- Building the Ontology2.1- Ontology Capture – Identify key concepts and relationships. – Produce clear text definitions for these concepts (i.e., glosses). – Identify terms that refer to these concepts. – Reach Consensus (Consensus is an indication of correctness).  You may apply the 7 steps for building an ORM schema, somehow!2.2- Ontology Coding/Specification/Characterization – Explicit representation of the “conceptualization” in some formal language. PalGov © 2011 11
  • 2.1- Ontology Capture: Scoping• Brainstorming – Produce all potentially relevant terms and phrases. • Nouns form the basis for concept names • Verbs (or verb phrases) form the basis for property and names. This step can be semi- automated somehow, as candidate concepts and relations can be extracted automatically from relevant documents, laws, forms, DB schemes....• Organize candidate concepts into groups Group related terms together. – Exclude some terms if not relevant (w.r.t., purpose and scope) – Keep notes of these decisions. – Group similar terms and potential synonyms together. PalGov © 2011 12
  • 2.1- Ontology Capture: Produce Definitions• Use suitable meta-ontology – i.e., use modeling primitives in a consistent manner (e.g. Type, role, entity, instance, relationship...)• When several people are involved, each might be responsible on a group of terms – Semantic overlap with others must be right in the first place, otherwise lot of redundant re-working.• Terms: Produce definitions/glosses in a middle-out fashion – Define a gloss for each term. This helps get deeper understanding of the domain. – These glosses will have to be revised later, after defining the relationships/ subsumptions between concepts. – This is called middle-out, rather than top-down or bottom up. – will be discussed later. PalGov © 2011 13
  • Define Taxonomy• Relevant terms must be organized in a taxonomic hierarchy (i.e., subsumptions) – Opinions differ on whether it is more efficient to do this in a top- down or a bottom-up fashion.• Ensure that hierarchy is indeed a taxonomy: – If A subsumes B, then every instance of A must also be a subsume B (compatible with semantics of rdfs:subClassOf) – Insuring the correctness of subsumptions needs philosophical thinking (apply the OntoClean Methodology).• The semantics of subsumption demands that whenever A subsumes B, every property that holds for instances of B must also apply to instances of A (called inheritance). – It makes sense to attach properties to the highest class in the hierarchy to which they apply. PalGov © 2011 14
  • Define Properties• Determine the relevant properties for each concept. Such properties must be essential –to describe the meaning-, or relevant to the applications.• While attaching properties to concepts, it is useful to determine its range (its datatype/value, or relations with other concepts). PalGov © 2011 15
  • Add Rules and Restrictions• Cardinality Restrictions• Which properties should be unique, mandatory, disjunctions, restricted values…etc.• Relational Characteristics – symmetry, transitivity, inverse properties, functional values  You must avoid the situation that the added rules are DB integrity constraints.  Some/all rules should be verbalized –in pseudo natural language sentences- so to enable other people review it and give feedback. PalGov © 2011 16
  • Define Some Important Instances• Some important instances (might) be added to the ontology, if needed. Such entities can be: – Country: Palestine – Person: Arafat – Capital: Jerusalem•  in case of a large instances, it is more convenient to have them separately . - See the Entity and Address servers in Zinnar PalGov © 2011 17
  • Advantages of the Middle-out Approaches• A bottom-up approach results in a high degree of detail – increases overall effort – makes it difficult to spot commonality between related concepts. – increases risk of inconsistencies and re-work.• Top-down allow better control of degree of detail – risk of arbitrary high-level categories – risk of limited stability• Middle-out strikes is a compromise, but it allow the ontology evolve gradually, you need to come back to some steps.• The higher level concepts naturally arise and are thus more likely to be stable. PalGov © 2011 18
  • Reaching Agreement: Some suggestions Ontologies are made to be agreed and shared, thus it is VERY important to make sure that people agree on them. How to facilitate reaching agreement?• Produce a natural language text definitions. - Ask domain experts to review the context, glosses, verbalized rules, and the ontology itself in a graphical/diagramatic form.• Ensure consistency with terms already in use – use existing thesauri and dictionaries – avoid introducing new terms in the definitions• Indicate relationships with other commonly used terms – synonyms, variants, such referring to different dimensions• Give examples PalGov © 2011 19
  • Integrating Existing Ontologies• Check overlap with existing ontologies• Establish formal links – Produce mappings to existing concept definitions – Import and extend existing ontologies• Avoid re-inventing the wheel! PalGov © 2011 20
  • Ontology EvaluationSeveral Type of evaluations: 1. Usability Evaluation: Validate whether the ontology produced satisfies (at least) the intended applications’ requirements. 2. Syntax evaluation: Validate whether the ontology is well-formed w.r.t the used language. 3. Logical evaluation: Validate whether the ontology has axioms contradicting or implying each other. 4. Ontological Evaluation: Validate whether the ontology has concepts that should be instances, sub-concepts that should be roles, etc. (The OntoClean methodology is very good for this evaluation) PalGov © 2011 21
  • Check for Implications and ContradictionsSome tools exist to automatically detect logical correctness (contradictionsand implications), depending on the used ontology language (Such as ORM:DogmaModeler, OWL: Racer) PalGov © 2011 22
  • Some GuidelinesClarity: The ontology engineer should communicate effectively with the domain experts (= ask the right questions): – Natural language definitions. – Give examples, alternatives, and contradictions, elicit knowledge. – emphasize distinctions.Coherence: The ontology should be internally consistent – Syntactically correct. – Logically consistent. – Ontologically consistent.Extensibility: modularize the ontology in a way it is easy to build, understand, and maintain. What should be in a module?Reusability and Usability: be innovative to tradeoff this smartly. PalGov © 2011 23
  • ReferencesMike Uschol: Building Ontologies: Towards a Unified Methodology.Proceedings of Expert Systems th Annual Conferenceof the British Computer Society Specialist Group on Expert Systems. 1996http://www.imamu.edu.sa/Scientific_selections/Documents/IT/96-es96-unified-method.pdfMustafa Jarrar: Towards methodological principles for ontologyengineering. PhD Thesis. Vrije Universiteit Brussel. (May 2005)http://www.jarrar.info/phd-thesis/Fernández López: Overview Of Methodologies For Building Ontologies.Proceedings of the IJCAI99 Workshop on Ontologies andProblemSolvingMethods Lessons Learned and Future Trends CEURPublications.http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.39.6002 PalGov © 2011 24