Semantic Web for Earth and Environmental Terminology (SWEET) Rob Raskin NASA/JPL July 20, 2006

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Semantic Web for Earth and Environmental
Terminology(SWEET)Rob RaskinNASA/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 Variable t time
Data quality 5
Lets eat, Grandma. Lets eat Grandma.
Time flies like an arrow. Fruit flies like a pie.
LA Times headline
Major combat operations in Iraq have ended
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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
• EarthSciencegtMeteorologygtWeatherPersonalitiesgtDave
  Jones
• 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
  (ltbgt lt/bgt pair gt 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

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SWEET Ontologies
Integrative
Earth Realm
Natural Phenomena
Physical Processes
Physical Properties
Human Activities
Substances non-living
Data
Substances Living
Auxiliary
Time
Space
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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Fragment of SWEET
3DLayer
subClassOf
PlanetaryLayer
partOf
primarySubstance air
Atmosphere

partOf
AtmosphereLayer
upperBoundary 50 km
subClassOf
subClassOf
sameAs Lower Atmosphere
lowerBoundary 15 km
Troposphere
Stratosphere
isUpperBoundaryOf
isLowerBoundaryOf
Tropopause
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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 EarthRealm Process, Phenomena Substance
Data
Time
SWEET
import
Stratospheric Chemistry
Biogeochemistry
Specialized domains
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Earth Science Ontologies

• Numerics are limited
• No Cartesian product (multidimensional) space
  predefined
• No numeric relations (, lt, gt, )
• 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