An STC "when" and "where" example

[Alasdair Allan]

Arnold Rots wrote:
> What you have there is not a valid document.

Pity! Why not? Where does it fall over?

> I'm a bit puzzled, though, why someone would want to use VOEvent to
> just transmit a position...

It's fairly fundamental. If I'm sending an alert that is going to
>  might as well send e-mail saying:

Email? For most purposes a VOEvent object will be serialised into an 
XML document and pushed over a SOAP connection

> "RA, Dec: 148.88821 69.06529"
> I would have thought that providing a time,

Time isn't necessary under all circumstances.

> wavelength,

Wavelength isn't necessary under many circumstances.

> observer's location,

Not necessary in many circumstances.

> and errors would be essential.

Errors are always helpful, but not necessary in all cases.

> STC-X does not allow defaults, in general, the reason being
> demonstrated by what you wrote: those defaults sounded very reasonable
> to you, but I would have chosen rather different ones.  Since the VO
> intends to tie together many subcommunities, the use of defaults is
> dangerous.

Defaults are necessary, the defaults can be specified as part of the 
standard and therefore everyone uses the same defaults and there is no 
danger.

> Giving minimal, sketchy information may be fine for some of your
> clients because they know exactly what you mean or they don't require
> great accuracy, but there may be other potential clients who cannot do
> anything with it because there isn't enough information; the planetary
> community is an obvious example.

Then they should ignore the document as it doesn't have enough 
meta-data for their purposes, those clients that can make use of the 
document can do so...

> As to your stripped-down version, I can make a similar one that is
> valid by using XIncludes and I have appended that one at the end of
> this message.  Three more lines than yours, one of which I promise to
> get rid of in the next version of the schema.

That looks a bit better, although I still don't understand your 
instance on including bandpass information for a time and co-ordinate 
representation.

> Any parser that feels like it (or knows what they say) can skip the 
> included documents which are going to be part of a standard IVOA 
> library.

Sorry, I have to take issue with this...

Are you going to sit down and write factory and parser toolkits in 
Perl, Python, Ruby, C, C++, C#, Fortran, Java, PHP and the half dozen 
other languages currently in use inside various projects that will be 
involved in creating and parsing VOEvent messages?

Just because the majority of the VO was written in Java doesn't mean 
the whole world uses Java. VOEvent is designed to go outside the 
carefully crafted VO infrastructure. People who have never heard of the 
VO might be interested, for the first time, in some of the stuff we're 
doing here. The buy-in for VOEvent has to be small, minimal.

Al.