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Ontology Best Practices: Experiences with SWEET

Ontology Best Practices: Experiences with SWEET. Rob Raskin NASA/Jet Propulsion Laboratory Pasadena, CA. Why an Upper-Level Ontology for Earth System Science? Why cooperate?. Many common concepts used across Earth Science disciplines (e,g, Temperature, Pressure)

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Ontology Best Practices: Experiences with SWEET

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  1. Ontology Best Practices: Experiences with SWEET Rob Raskin NASA/Jet Propulsion Laboratory Pasadena, CA

  2. Why an Upper-Level Ontology for Earth System Science?Why cooperate? • Many common concepts used across Earth Science disciplines (e,g, Temperature, Pressure) • Provides common definitions for terms used in multiple disciplines or communities • Provides common language in support of community and multidisciplinary activities • Provides common “properties” (relations) for tool developers • Reduced burden (and barrier to entry) on creators of specialized domain ontologies • Only need to create ontologies for incremental knowledge

  3. Role of Upper Level Earth Science Ontology Math Physics Chemistry General domains Space import Property PlanetaryRealm Process, Phenomena Substance Data Common Earth elements Time import Stratospheric Chemistry Biogeochemistry Specialized domains

  4. Semantic Web for Earth and Environmental Terminology (SWEET) • Concept space written in OWL • Initial focus to assist search for data resources • Funded by NASA • Later focus to serve as community standard • Enables scalableclassification of Earth system science concepts • Populated initially with GCMD, CF concepts (decomposed)

  5. SWEET 1.0 Ontologies (and their interrelationships) Faceted Ontologies Living Substances Non-Living Substances Integrative Ontologies Natural Phenomena Physical Processes Human Activities Earth Realm Data Physical Properties Space Time Units Numerics

  6. SWEET 2.0 • Same facets, but organized by subject • 12 ontologies --> 100 ontologies • Easier for domain specialists to build self-contained specialized ontologies that extend existing ones

  7. SWEET 2.0 Ontologies Importationt

  8. Common Issues • Units • UDUnits • Standard math • Ordered pairs and triples, arithmetic operations • Intervals • hasLowerBound, hasUpperBound, hasUnit • Provenance • Sequence of steps • Fuzzy concepts • nearlySameAs, similarityMeasure [0…1]

  9. Best Practices (1): • Identify characteristic level of abstraction of each term • If multiple definitions/levels (e.g., “climate”), repeat in multiple ontologies (namespaces) • Keep ontologies small, modular • Be careful that “Owl:Import” imports everything • Use higher level ontologies where possible • Identify hierarchy of concept spaces • Try to keep dependencies unidirectional

  10. Best Practices (2): • For synonyms, identify (community, preferred term) pairs • Gain community buy-in • Involve respected leaders • Most ontologies can be faceted • Holistic ontologies can be layers/wrappers atop faceted ontologies

  11. Best Practices (3): • Use OWL individuals (instances) sparingly • Assume OWL-DL will be used, because most tools cannot support OWL-Full • Typically, a data collection is a “class” and a component of the Earth is a class • A particular observation at a specific time is a “state” (of the planet) which could be an individual • OWL has limited capabilities • Instructions to reasoners can be included (e.g., “multiply”) • Collect suggestions for implementations in future versions, or an OWL-Sci package

  12. Community Issues • Review Board • Who will oversee and maintain for perpetuity (or at least through the next funding cycle) ESSI? • Content • Maintain alignment given expansion of classes and properties • No removal of terms except for spelling or factual errors • Subscription service to notify affected ontologies when changes made • Must avoid contradictions • Additions can create redundancy if sameAs not used • Humans must oversee “matching” • CF has established moderator to carry out analogous additions

  13. PlanetOnt.orgCollaboration Web Site • Discussion tools • Blog, wiki, moderated discussion board • Version Control/ Configuration Management • Trace dependencies on external ontologies • Tools to search for existing concepts in registered ontologies • Ontology Validation Procedure • W3C note is formal submission method • Registry/discovery of ontologies • Support workflows/services for ontology development

  14. PlanetOnt.org

  15. ESIP Federation

  16. PO.DAAC Knowledge Bases Public access Documents People Roles/Tasks Data Processing Data Products Metadata Tools/ Services Web Pages Science Concepts Missions Instruments Organiza- tions Applications Announce- ments Inquiries Computers

  17. Resources • SWEET • http://sweet.jpl.nasa.gov • Ontology development/sharing site • http://PlanetOnt.org • Noesis (search tool) • http://noesis.itsc.uah.edu • SESDI • http://sesdi.hao.ucar.edu

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