Expressing position in RDF
bernard.vatant at mondeca.com
Tue Oct 14 01:25:29 PDT 2008
Have been lurking at this conversation so far. Some thoughts below,
about this very generic use case in science : how do you attach
measurement results to an object? Seems to me the scientific community
(at least its members involved in Semantic Web) should try and
standardize this at some point. I've been looking for relevant pointers
to people working on this in other domains (say e.g., Biology, Earth
sciences ...) without much success so far I'm afraid. Of course hoping
astronomers would be leaders in such a process :-)
> Although this works, it is very verbose for such a simple (!)
> statement. To sell this sort of stuff to end users, we really need a
> practical and succinct set of object properties that would allow me
> just to do:
> :MyObject a:rightAscension 134.556^^xsd:float
1 : "object properties" might be confusing in this conversation context.
I guess you mean "properties of objects", not "ObjectProperty" in the
OWL sense ... since actually your a:rightAscension would be a datatype
2 : With such shortcuts, you don't assert the coordinate reference J2000
and the unit, so it is implicit, which is not a good idea ... or you
have to built-in the coordinate system and unit in the property ...
:MyObject a:rightAscensionJ2000In DecimalDegrees 134.556^^xsd:float
The problem with this is that it leads to a proliferation of properties,
and you can't in this case assert "properties of the property", such as
accuracy of the value, method of acquisition, and whatever relevant
description of the measure process ... Direct assertion is blurring the
fact that attaching a property-value pair to an object, in science, is
called a measurement, of which description must come along with the data
if those data want to be qualified as scientific data.
So it is not only a technical issue of representation, what is at stake
is what qualifies scientic data from simple property-value pairs. I
don't know which "end users" you have in mind, but there is a huge trend
in science outreach to hide all the data context to "simplify" the
presentation of data. See what I mean :-)
This is the local illustration of all the issues debated at length in
the Semantic Web community at large about trust, data quality etc.
Ed, for a simpler expression of your example, one can use nested blank
nodes for coordinates (it's indeed a typical use case of blank nodes)
and I don't think either asserting the class of those nodes is really
useful, nor specifying a URI. Merging or matching of such information
would in any case drill down to the values. OTOH, I added the precision
of the data, and some Dublin Core metadata on the measurement. Which is
not possible to add using the direct property on the object.
:MyStar a a:star;
_:b1 geo:hasCoordinate _:myRA.
_:b1 dc:source :MyCatalog
_:b1 dc:date "2008-10-14:00.00"
_:myRA a a:rightAscension;
>> On Oct 13, 2008, at 7:24 PM, Ed Shaya wrote:
>>> Here is "MyStar has a J2000 RA of 34.5343 degrees, it would be
>>> something like this in N3:
>>> :MyStar a a:star;
>>> ivoa:hasPosition :MyCoordinates.
>>> :MyCoordinates a
>>> geo:hasCoordinate :myRA.
>>> :MyRA a a:rightAscension;
>>> q:hasFloat 34.5343^^xsd:float;
>>> q:hasUnits ui:degree.
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