VOEvent session

[Roy Williams]

>> Note that 'utype' is never used in the v2.0 spec, and 'data model'
>> is used only in describing a<Reference>, I'm not sure where your
>> argument is going with that.

> It's interesting to see where the VO "vision" is going.  In 2005,
> "XML Schema" was the answer to all questions.  Rather, now folks
> suggest that actually building a Schema as complex as the underlying
> data is unacceptable.  Instead we are supposed to have a simple
> Schema - perhaps just a sequence of Params - but with utype
> attributes that map (not clear if this is either surjective or
> injective) onto some ideal data model.  The complexity is now all in
> the utypes, and validating against the Schema doesn't actually tell
> you anything about the contents of the file.

My favorite data model is the complex number, with a data model of Real 
and Imaginary components. Here are some representations of the number 
z=1+2i. The advantage of (1) is automated code binding and document 
validation. The advantage of (2) is flexibility and encoding validity in 
a non-XML layer. The advantage of (3) is simplicity and conciseness.

(1) "Pure" XML
<complex name="z">
   <real>1</real>
   <imag>2</imag>
</complex>

(2) Impure XML a la VOTable, VOEvent
<Group name="z" type="complex">
   <Param name="zr" utype="complex.real" value="1"/>
   <Param name="zi" utype="complex.imag" value="2"/>
</Group>

(3) JSON
{"z": {"zr":1}, {"zi":2}}