Ontology Best Practices: Experiences with SWEET

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Ontology Best Practices Experiences with SWEET

• Rob Raskin
• NASA/Jet Propulsion Laboratory
• Pasadena, CA

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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

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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
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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 scalable classification of Earth system
  science concepts
• Populated initially with GCMD, CF concepts
  (decomposed)

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SWEET 1.0 Ontologies (and their
interrelationships)
Faceted Ontologies
Non-Living Substances
Living Substances
Integrative Ontologies
Physical Processes
Natural Phenomena
Earth Realm
Human Activities
Physical Properties
Data
Time
Space
Units
Numerics
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SWEET 2.0

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

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SWEET 2.0 Ontologies
Importationt
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Common Issues

• Units
• UDUnits
• Standard math
• Ordered pairs and triples, arithmetic operations
• Intervals
• hasLowerBound, hasUpperBound, hasUnit
• Provenance
• Sequence of steps
• Fuzzy concepts
• nearlySameAs, similarityMeasure 01

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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 OwlImport imports everything
• Use higher level ontologies where possible
• Identify hierarchy of concept spaces
• Try to keep dependencies unidirectional

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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

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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

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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

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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

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