1. The state of VOEvent semantics THE US NATIONAL VIRTUAL OBSERVATORY
Matthew J. Graham (Caltech, NVO)
IVOA Strasbourg: Semantics I
26 May 2009

2. What is semantics important?
Transient astronomy suffers from:
heterogeneous data
distributed data
x-scale data
Humans are:
slow
expensive
non-algorithmic
untrustworthy
Semantics makes data machine-processible so computers can do the grunt work
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3. Semantic technologies
RDF (Resource Description Framework):
a family of W3C specifications for conceptual modelling
a fact is a subject-predicate-object triple
various serializations: RDF/XML, RDFa, N3
Concept schemes:
controlled vocabularies
taxonomies
ontologies
Knowledge bases:
triple/quad store
relational db with a suitable front end (e.g. d2r)
SPARQL
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4. De Vorerum Natura The VOEvent specification states:
“The <What> and <Why> elements work together to characterize the nature of a VOEvent”
Specific semantic components:
<What>:
<Param name=“” value=“” ucd=“” unit=“”/>
<Group name=“”>
<Why>
<Concept>…</Concept>
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5. Control your language What: Why:
Register data dictionaries used by event authors:
SkyAlert
VO registry (part of VOEventStream registry extension)
Group name + Param name must be unique
Why:
Transients classification scheme from dotastro.org
Astronomical object type ontology from CDS/EuroVOTech
Transients ontology from Caltech
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6. dotastro.org
128 classes
Based on GCVS
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7. ObjectType ontology ~80 variable classes Multiple inheritance
Properties
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8. Transients ontology
 231 classes
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9. Looking for domain experts
If interested in contributing scientific domain knowledge, please contact:
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10. Managing followup information
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11. Contextual technologies
Linked Data – connects two URIs with an owl:sameAs: same individual with same identity
UMBEL – a lightweight subject concept reference structure; an infocline
OAI ORE – describes aggregations of Web resources
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12. Data portfolio
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13. Summary
In the era of data intensive astronomy (Astronomy 2020), semantic technology (astroinformatics) provides the structural underpinnings for doing science
Bulk of data activities will be performed by intelligent agent systems
Continuing efforts to develop usable ontological structures
Looking for domain experts:
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