some semantic puzzles from VOEvent

Fri Jun 3 06:00:08 PDT 2005

Just an addition after eventually finding out the VOEvent schema ...
http://www.ivoa.net/internal/IVOA/IvoaVOEvent/VOEvent-0.90.pdf

... good to see everything I wrote below is mostly useless, since it's all in that
document, basically. Sorry for the noise.
So either I missed the point of the questions, or their point is the difficulty to see the
articulation of the ontology with the data schema, e.g. how many entities, and of which
type is a VOEvent (as a data set) about. In the latter case, maybe what I wrote is worth
reading.

Bernard

> -----Message d'origine-----
> De : owner-semantics at eso.org [mailto:owner-semantics at eso.org]De la part
> de Bernard Vatant
> Envoye : vendredi 3 juin 2005 10:46
> A : semantics at ivoa.net
> Objet : RE: some semantic puzzles from VOEvent
>
>
>
> Some suggestions of tracks to answer Roy's puzzles ...
>
> (1) Adding an interpretation to a VOEvent. In the VOEvent schema, we have a
> "Why" section
> where the publisher can say what they think the event is (supernova or an outburst of a
> variable star or a microlensing event or GRB etc etc). We would like a formal vocabulary
> so that, for example, the computer can understand that "Supernova" and "SN" are the same
> thing. However, my simple attempts to do this as a new branch of the UCD tree
> blew up into
> a storm of controversy. How can we make progress here?
>
> BV : Preliminary question : I've mined the whole IVOA website looking for
> VOEvent schema,
> but could not find it. Is it available somewhere? Even as a draft?
> Seems to me that a science ontology should always make distinct the
> representation of the
> *experimental data* (which if I get it right, are what VOEvent(s) are about), and
> *interpretations* of those data. The word "event" is overloaded here, since it seems to
> encapsulate both, hence the difficulty, frequent in science. Although everyone
> involved in
> experimental science is aware (or should be) in theory of this distinction, in practice
> it's often forgotten when there is global implicit agreement on interpretation.
> When I say
> : "This is an infrared image of the planet Jupiter" I somehow forget the distinction. I
> should say : "This is the result of a process in which X have gathered bytes using such
> telescope, CCD, software ... and that Y interprets as being an image in IR of the planet
> Jupiter". But nobody would do that in that case, because everybody knows (or
> thinks so) or
> at least implicitly agrees upon what Jupiter *is* and looks like, what a planet
> *is*, and
> so on. There is a unique (implicit) interpretation in the common (implicit) ontology. Of
> course, this breaks for SN or GRB, where the question of interpretation is
> critical. I've
> an old Web Page about that issue [1].
>
> If one wants to clarify and formalize, this distinction has to be captured in the
> ontology. The way I see it, roughly and non-exhaustive, and independently of
> specific data
> or even scientific domain (this applies also in Biology, Earth Sciences, whatever). An
> "Event" is composed of one "Fact" and one or more "Interpretation(s)". When I
> say "Fact",
> read "experimental fact".
>
> Components of Fact
> 	What : Data Set (including values, units etc ...)
> 	When - Where : Space-Time location of the experiment
> 	How : Tools (Method, Instrument, Protocol ...)
> 	Who : Actor in the Fact (observer, data curator ...)
> 	Related Facts : Previous, Follow-up
> 	Framework : Research Program ...
> 	Why : Purpose of the event (why the data have been gathered for,
> hypothesis, whatever)
> 	...
>
> Components of Interpretation
> 	Science Object : The thing(s) data are about, and their type
> 	Model (this is more tricky : includes theoretical framework, world model, ...)
> 	Who : Who makes the interpretation
> 	Publication : Various material documenting the interpretation
> 	Support : Other facts and interpretations contributing to the interpretation
> 	Similar : Other facts interpreted as being about the same object
> 	...
>
> I would be happy to propose a more formal description of all that in a OWL
> format if folks
> are interested to review it.
>
> (2) Suppose we have a collection of Event observation packets *that are all about single
> astrophysical event*, but made by different people from different telescopes. How can I
> look at the interpretations ("Why" sections) and decide if there is a difference of
> opinion, or a change in interpretation with time? One report says the Event is a
> Supernova, another says it is a SupernovaType1a, another says it is a SN and
> another says
> "bright source associated with a galaxy". Are these four in agreement?
>
> BV : I've underlined *that are all about single astrophysical event*. Think about the
> meaning of this sentence at the light of the above distinction. You have different
> experimental facts, interpreted as being about the same object. Observer X has taken an
> image later interpreted as being a SN 1c in NGC 4038. Other, looking to the same sky
> coordinates, have obtained other data that they interpret as being images of the "same"
> object in the "same" galaxy (whatever this "sameness" actually means ...). The
> "object" is
> named 2004gt. Looking at some description :
> http://www.rochesterastronomy.org/supernova.html#2004gt ... the distinction between the
> fact and the interpretation is far from obvious.
>
> Now to answer directly your question about agreement, seems to me that there are three
> levels of agreement:
> 1. Agreement about speaking of the same fact(s) - same observation(s)
> 2. Agreements about interpretation :
> 	2.a : Agreement on "sameness" of object across different observations
> 	2.b : Agreement on type of this object
> For all those, all the point is to explicitly identify the subject of conversation.
> Agreement between SN and SN 1c interpretations can be inferred if the ontology
> of objects
> declares that SN 1C is a subclass of SN.
>
> (3) In VOEvent, there is a section for saying what was measured, and it is a
> collection of
> parameters that are characterized by UCD. For example PEAK_COUNT=3243 and R-MAG=17.5 and
> BANANA_FLUX=4.654. If I have a lot of VOEvent packets that refer to the same
> astrophysical
> event, can I extract a SED or light-curve (or time-dependent SED) by federating all the
> separate observations?
>
> BV: The answer is "yes" if the "what was measured" refers to an interpretation with
> agreement on 2.a (in terms of object sameness). When I extract a light-curve I am in the
> framework of interpretation. I mean there is no light-curve that is a fact, unless it's
> directly captured by a single instrument, protocol ... As long as you put together data
> from different sources, the agreement about those data being about the same
> thing supposes
> an (there again, most of the time implicit) agreement on a world model where this object
> is supposed to "exist".
>
> This seems somehow independent of any agreement on 2.b (type of the object)
> although it's
> not obvious that there can be any agreement on the sameness of an object if there is
> disagreement on its type. From a formal viewpoint, suppose you have declared in the
> ontology that SN 1a and SN 1c are disjoint subclasses of SN, if interpretation
> X says that
> E is instance of SN 1a and interpretation Y says that E is instance of SN 1b, but agree
> that E is the same object (same object identification), I can infer that X and Y are
> inconsistent (read : disagree).
>
> Hope that is helpful, and not adding to confusion :))
>
> [1] http://perso.wanadoo.fr/universimmedia/subjects.htm
>
> **********************************************************************************
>
> Bernard Vatant
> Senior Consultant
> Knowledge Engineering
> bernard.vatant at mondeca.com
>
> "Making Sense of Content" :  http://www.mondeca.com
> "Everything is a Subject" :  http://universimmedia.blogspot.com
>
> **********************************************************************************
>
>
>