Ontology of
Astronomical Object Types
Alexandre RICHARD (INAF)
Sébastien DERRIERE (CDS)
Andrea PREITE MARTINEZ (INAF)
InterOpMay2007
Summary
• An ontology of object types
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What is an ontology?
What's a defined concept?
How to deal with ~
Present status
• Use cases
– Registry Request Builder
– Concept Explorer
May 17th, 2007
InterOpMay2007
2
What's an ontology?
• a data model of a given domain
• a repository of knowledge, logically organized, exploitable by
a “reasoner”
• a “formal representation of a conceptualization”
• “a description of the concepts and relationships that can exist for
an agent or a community of agents” generally written “as a set of
definitions of formal vocabulary.”
The present ontology is:
• made of defined concepts of astronomical objects
• formalized using description logics & implemented in OWL 1.1
• edited with Protégé and exploited with the Protégé-OWL API
InterOpMay2007
What's a defined concept?
To define a concept:
transform knowledge into relationships and necessary
and/or sufficient conditions
SN Type Ia:
n&s is-a SNTypeI (is-a SN)
is-a StellarObjectInDoubleStar
hasProgenitor some AccretingWhiteDwarf
inh
hasVariabilityProcess some SuperNovaExplosion
hasProcess some ThermonuclearFusion
inh
not (hasAbsorptionSpectralLine has ElementH)
n&s hasAbsorptionSpectralLine has ElementSi
InterOpMay2007
I
Rn
processes
R1
R2
C1
measurements
Properties
N/S?
is-a
C
C2
R3
R4
components
InterOpMay2007
morphology
Dwarf Nova
• hasMeasurement has VariabilityTimeScale-sevDayssevMonths
• hasMeasurement has FluxAmplitudeVariation-GT1
• hasMeasurement has Period-0.05-0.5d
• hasPortion some AccretionDisk
• is-a CataclysmicVariable
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–
–
–
–
DoubleStar
hasMorphology some Close
hasComponent some WhiteDwarf
hasComponent some ((Dwarf or SubGiant) and LateTypeStar)
hasVariabilityProcess some Explosion
InterOpMay2007
How to deal with:
...there is often an accretion disk...
...almost all are observed in the IR...
C1
hasEmissionIn
all IR sources
isEmittedBy
some are
IR sources
C2
C3
InterOpMay2007
IR
Ontology Construction
• Identifying concepts & properties
– Total: 263, AstroObj: 175
– 26 properties
• Defining concepts
– 86 with necessary and sufficient conditions
• Building the subsumption hierarchy
– Concept hierarchy
– Property hierarchy
• Adding annotations
• Testing efficiency
May 17th, 2007
InterOpMay2007
Consistency
check
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Registry request builder
• Registry query with the ontology
– The resource description in the registry is fuzzy
(<subject> content is free)
– The queries expressed by the user must be flexible
– The ontology of object types is not used to classify individual
sources, but to organize the relationships between classes.
– It is therefore used to achieve an intelligent recovery of
resources related to one object class
May 17th, 2007
InterOpMay2007
9
Concept Explorer
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•
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Compare a new concept to existing ones
Get concepts with given property
Explore (browse) knowledge
Test consistency
May 17th, 2007
InterOpMay2007
10