An OWL Compiler

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					Semantic Web for Earth and
Environmental Terminology
        (SWEET)
        Rob Raskin
        NASA/JPL

         July 20, 2006
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                   Outline
   Why use ontologies?
   SWEET ontologies
   Update/community processes




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Why Use Ontologies?




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Semantic Understanding is Difficult!
           Sea surface temperature: measured 3 m above surface
           Sea surface temperature: measured at surface
Variable t: temperature               Data quality= 5
Variable t: time


        Let’s eat, Grandma.
        Let’s eat Grandma.

  Time flies like an arrow.
  Fruit flies like a pie.
                                           LA Times headline

            Major combat operations in Iraq have ended               F
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                           Ontologies

   General definition: “all that is known”
   Computer science definition: Machine-readable definition of
    terms and how they relate to one another
       As with a dictionary, terms are defined in terms of other terms
   Provide shared understanding of concepts
   Enable deeper semantics than typical controlled vocabulary for
    machine-to-machine communications




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              Taxonomy vs. Ontology
   Taxonomy (librarian perspective)
      Subject Classification

      Children are subcategory, not necessarily subclass of parent concepts

      Example:

             EarthScience>Meteorology>WeatherPersonalities>DaveJones
        Used by: Library of Congress, Dewey Decimal System, Web
         OpenDirectory, GCMD Keyword

   Ontology (knowledge engineer perspective)
      Children are subclasses of parent concepts

          Parent properties inherited by children

          Multiple inheritance generally supported

      Scalable

          “New” concepts are often definable using multiple inheritance
           (e.g. Sea floor temperature) rather than creating a new definition
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XML-based Ontology Languages
   XML satisfies desired properties for language syntax
   However, there are too many possible ways that XML tags can
    be named and used
   No standardization of XML tag meanings as in HTML (<b>
    </b> pair => renders in bold)
   Additional standardized semantics needed to exploit shared
    understanding of concepts
   W3C has adopted specializations of XML that predefine
    particular tags
       Resource Description Formulation (RDF)
       Ontology Web Language (OWL)


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            Semantic Web Vision
   Web page creators place XML tags around
    technical terms on web pages
   XML tags point to ontology where term is
    defined
   Search tools use this information to provide
    value-added services
       Common search engines (Google) use these
        capabilities only minimally, at present

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                          Applications
   Software tools can find “meaning” in resources for
       Discovery
       Fusion
       Lineage
       …
   Requirements
       Data products associated with objects in “science concept space”
            Richer descriptions than DIFs
       Data services associated with objects in “service concept space”
            Richer descriptions than SERFs
       Search/fusion tools that exploit ontologies


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SWEET Ontologies




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                            SWEET

   Comprehensive upper-level ontology of Earth system science
    concepts
   Initial emphasis on improving search for NASA Earth
    science data resources
   Provides common semantic framework for representing Earth
    science data, information and knowledge
   Populated manually initially from:
        GCMD controlled and uncontrolled keywords
        CF terms



    Funding provided by the NASA Earth Science Technology Office         F
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             SWEET Ontologies
Integrative
                                          Earth Realm
  Natural
Phenomena                                  Physical
                         Physical
                        Properties         Processes
 Human
Activities                                Substances
                                          non-living

  Data                                    Substances
                                            Living


                       Auxiliary

    Space       Time            Units   Numerics
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    SWEET is a Concept Space
   Enables scalable classification of Earth science and associated
    data concepts
   Captures scientific philosophies
      Reductionism (in orthogonal, facted ontologies)

      Holisism (in integrative, unifying ontologies)

   Uses standard language (OWL DL)
      Enables domain specialists to expand and specialize the
       work of others
      Enables concepts to be translatable into other
       languages/cultures using “sameAs” notions
      Enables use of reasoners and other standard ontology tools



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3DLayer
subClassOf               Fragment of SWEET
   PlanetaryLayer
       partOf
                           primarySubstance
             Atmosphere    =“air”
              partOf
                      AtmosphereLayer
                                                 upperBoundary
sameAs=             subClassOf   subClassOf      =50 km
“Lower
                Troposphere       Stratosphere   lowerBoundary
Atmosphere”
                                                 =15 km
             isUpperBoundaryOf   isLowerBoundaryOf

                          Tropopause                          F
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        Science Ontology Classes
   Earth Realms
       Atmosphere, SolidEarth, Ocean, LandSurface, …
   Properties (includes default unit)
       temperature, composition, area, albedo, …
   Substances
       CO2, water, lava, salt, hydrogen, pollutants, …
   Living Substances
       Humans, fish, …
   Processes
       Diffusion, absorption, …

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    Integrative Ontology Classes

   Phenomena
       ElNino, Volcano, Thunderstorm, Deforestation)
       Each has associated EarthRealms, PhysicalProperties,
        spatial/temporal extent, etc.
       Specific instances included
            e.g., 1997-98 ElNino
   Human Activities
       Fisheries, IndustrialProcessing, Economics, Public Good
   History
       State of planet or equipment

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          Data Ontology Classes
   Dataset characteristics
       Format, data model, dimensions, …
   Special values
     Missing, land, sea, ice, ...
   Parameters
       Scale factors, offsets, …
   Data services
       Subsetting, reprojection, …
   Quality measures
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                Properties
   Intervals
      hasUpperLimit, hasLowerLimit,
       hasUnit
      Applicable to spectral range and
       vertically structured layers of the Earth
   Spatial relations
      northOf, above, insideOf, hasDirection

   Other numerical relations
      hasCoordinate1, lessThan
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           SWEET is Middleware
   The intention is for specialized user communities to
    extend its content
   SWEET provides the common sense knowledge of
    Earth system science that is common to all disciplines
   Domain specialists need to add only the incremental
    knowledge over and beyond the basic Earth system
    science knowledge
   Community can submit extensions back into SWEET
       “sameAs” tags can be tagged with your community name

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        SWEET as an Upper Level
         Earth Science Ontology
         Math      Physics   Chemistry

Space     import
                      Property
Time                EarthRealm     SWEET
                Process, Phenomena
                     Substance
                        Data
                             import
          Stratospheric   Biogeochemistry   Specialized
           Chemistry                        domains             F
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         Earth Science Ontologies
   Numerics are limited
       No Cartesian product (multidimensional) space
        predefined
       No numeric relations (+, <, >, …)
   Community conventions must standardize
    extensions to language



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Update/Community
    Processes



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               SWEET Users
   ESML- Earth Science Markup Language
   ESIP - Earth Science Information Partner Federation
   GEON- Geosciences Network
   GENESIS- Global Environmental & Earth Science
         Information System
   IRI- International Research Institute (Columbia)
   LEAD- Linked Environments for Atmospheric
         Discovery
   MMI- Marine Metadata Initiative
   NOESIS
   PEaCE- Pacific Ecoinformatics and Computational Ecology
   SESDI- Semantically Enabled Science Data Integration
   VSTO- Virtual Solar-Terrestrial Observatory
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         Community Objectives

   Enable domain specialists to use and extend
    SWEET content
   Enable SWEET ontology to be accepted as a
    community standard
   Submit SWEET to the NASA Earth Science
    Standards Process Group during 2007



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           Collaboration Web Site
   Basics
       Blog, wiki, moderated discussion board, version control,
        validation services
   Search across ontologies
   Trace of dependencies across ontologies
       RSS service to notify ontology developers when change
        has been made
       Policy is to remove term only if absolutely necessary, to
        remain backward compatibility
   Expansion into new domains
       Geology, upper atmosphere, hydrosphere
   Review board
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        For more information…
   http://sweet.jpl.nasa.gov




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