Upper-Level Ontologies for

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21 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

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SWEET:

Upper
-
Level Ontologies for

Earth System Science


OPeNDAP Meeting

Feb 2007


Rob Raskin

PO.DAAC

Jet Propulsion Laboratory



Data to Knowledge



Data




Information


Knowledge

Basic Elements

Bytes Numbers


Models


Facts

Services


Ingest Archive


Visualize Infer Understand Predict

Storage


File Database HDF
-
EOS GIS/MIS


Ontology Mind

Interoperability

Syntactic

OPeNDAP WMS/WCS


Semantic

Volume/Density

High/Low




Low/High

Statistics


Checksum Moments Descriptive

Inferential

Analysis



Fourier Wavelet EOF SSA

Methodology


Exploratory
-
analysis Model
-
based
-
mining

Syntax





Semantics

Semantics: Shared
Understanding of Concepts



Provides a namespace for scientific terms…plus


Provides descriptions of how terms relate to one another


Example tags in markup language:


subclass, subproperty, part of, same as, transitive property,
cardinality, etc.


Enables object in “data space” to be associated formally
with object in “science concept space”


“Shared understanding” enables software tools to find
“meaning” in resources


Ontology Representation


W3C has adopted four XML
-
based standard
ontology languages:


RDF, OWL
-
Lite, OWL
-
DL, OWL Full


Basic building blocks:


Class, subclass, property, subproperty, sameAs


Standard language enables anyone to extend
an ontology


Knowledge built up incrementally


Why an Upper
-
Level Ontology
for Earth System Science?



Many common concepts used across Earth
Science disciplines (such as properties of the
Earth)


Provides common definitions for terms used in multiple
disciplines or communities


Provides common language in support of community
and multidisciplinary activities


Reduced burden (and barrier to entry) on creators
of specialized domain ontologies


Only need to create ontologies for incremental
knowledge


Semantic Web for Earth &
Environmental Terminology
(SWEET)


Ontology of Earth system science and data
concepts


Provides a common semantic framework (or
namespace) for describing Earth science
information and knowledge


Emphasis on improving search for NASA
Earth science data resources


Represented in OWL
-
DL

Non
-
Living

Substances

Living

Substances

Physical

Processes

Earth Realm

Physical

Properties

Time

Natural

Phenomena

Human Activities

Integrative Ontologies

Space

Data

Faceted Ontologies

Units

Numerics

SWEET Ontologies

SWEET Supports

Knowledge

Reuse



SWEET is a concept space


Enables scalable
classification

of Earth science and data
-
related concepts


Enables object in data space to be mapped to science
concept space


Concept space is translatable into other
languages/cultures using “sameAs” notions


SWEET Science Ontologies



Earth Realms


Atmosphere, SolidEarth, Ocean, LandSurface, …


Physical Properties


temperature, composition, area, albedo, …


Substances


CO2, water, lava, salt, hydrogen, pollutants, …


Living Substances


Humans, fish, …

SWEET Conceptual Ontologies



Phenomena


ElNino, Volcano, Thunderstorm, Deforestation,
Terrorism, physical processes (e.g., convection)


Each has associated EarthRealms,
PhysicalProperties, spatial/temporal extent, etc.


Specific instances included


e.g., 1997
-
98 ElNino


Human Activities


Fisheries, IndustrialProcessing, Economics,…

SWEET Numerical Ontologies


SpatialEntities


Extents: country, Antarctica, equator, inlet, …


Relations: above, northOf, …


TemporalEntities


Extents: duration, century, season, …


Relations: after, before, …


Numerics


Extents: interval, point, 0, positiveIntegers, …


Relations: lessThan, greaterThan, …


Units


Extracted from Unidata’s UDUnits


Added SI prefixes


Multiplication of two quantities carries units


Numerical Ontologies


Numeric concepts defined in OWL only through
standard XML XSD spec


Intervals defined as restrictions on real line


Added in SWEET


Numerical relations (lessThan, max, …)


Cartesian product (multidimensional spaces)


Numeric ontologies used to define spatial and
temporal concepts



XSD: Datatypes


Numeric


boolean, decimal, float, double, integer,
nonNegativeInteger, positiveInteger,
nonPositiveInteger, negativeInteger, long, int,
short, unsignedLong, unsignedInt, unsignedShort,
unsignedByte, hexBinary, base64Binary


String


String, normalizedString, anyURI, token,
language, NMTOKEN, Name, NCName


Date


dateTime, time, date, gYearMonth, gYear,
gMonthDay, gDayxsd:gMonth



Data and Services Ontology


Formats


Data models


Data Sttructures


Special values


Missing, land, sea, ice, etc.


Parameters


Scale factors, offsets, algorithms


Data Services


Subset, reproject


Example: AIRS Level 2
Dataset


Subset of Dataset where


DataModel= Level 2


Instrument= AIRS


HorizontalDimension= 2


VerticalDimension= 1


Format= HDF
-
EOS


Property= Temperature


Substance= Air


Fragment of SWEET




Atmosphere

AtmosphereLayer

Troposphere

Tropopause

Stratosphere

isUpperBoundaryOf

isLowerBoundaryOf

subClassOf

subClassOf

partOf

PlanetaryLayer

partOf

3DLayer

subClassOf

upperBoundary

=50 km

lowerBoundary

=15 km

primarySubstance

=“air”

sameAs=

“Lower

Atmosphere”

How SWEET was Initially
Populated


Initial sources


GCMD


Over 10,000 datasets


Over 1000 keywords


Data providers submit additional terms for “free
-
text” search


CF


Over 700 keywords


Very long term names


surface_downwelling_photon_spherical_irradiance_in_sea_water


Decomposed into facets


Property= spherical_irradiance


Substance= sea_water


Space= surface


Direction= down

Collaboration 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


Community Issues


Content


Maintain alignment given expansion of classes and
properties


Standards and Conventions


Agreement on standards for use of OWL


Fuzzy representation conventions


Submit as standard to NASA Standards & Processes
Working Group


Review Board


Who will oversee and maintain for perpetuity (or at least
through the next funding cycle)?


ESIP Federation? A new consortium?


Global Support


Provide tools to visualize and appreciate the big picture

Update/Matching Issues


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


OWL “import” imports entire file


Associate community with ontology terms


Community tagging

Best Practices


Keep ontologies small, modular


Be careful that “Owl:Import” imports
everything


Use higher level ontologies where possible


Identify hierarchy of concept spaces


Model schemas


Try to keep dependencies unidirectional

Web Sites


http://sweet.jpl.nasa.gov


http://PlanetOnt.org