VOEvent - Param comment

[Roy Williams]

On Aug 7, 2006, at 6:54 AM, Petr Kubanek wrote:
> You are making in my point-of-view classical XML-designers mistake.

This is not a mistake, but on the contrary, there was a great deal of  
thought (and argument) went into it. This is a compromise between  
structure and flexibility.

The structured approach is
     <trigger_num>114299</trigger_num>
and the flexible approach is
    <Param name="trigger_num" value="114299" ucd="meta.id" />

The former is certainly easier for the computers to validate, and  
makes nicer code when the code-binding tools are used. But the  
problem here is that we don't know in advance what kind of  
measurements will be made. Perhaps one group measures something  
called "trigger_num", other VOEvent providers have other names for  
parameters. It would be very difficult for those providers to use a  
structured approach. There would be "extra" schemas for each dialect  
of VOEvent, the authors would need to build and document such a sub- 
schema, put the schema into a permanent web-accessible repository,  
and be careful with versioning every time it changes. The subscriber  
to such events would also have trouble bringing in the correct schema  
and validating it.

And there's the rub: the more effort we demand from authors, the less  
likely they are to become part of VOEvent.

> By letting free UCDs parameters you actually say: we don't care  
> about researching which ever possible events can be transported by  
> VOEvent,

No. We have said that in one part of the VOEvent there will be data  
whose structure we cannot know in advance, and that the structure  
there will change faster than our versioning process.

Perhaps you could help us in a constructive way by defining what kind  
of parameters the INTEGRAL instruments will be producing when they  
report an event. We would be happy to help you to add structure in  
the form of Group elements and UCDs.

When evaluating a VOEvent for possible follow-up, we see different  
approaches by different groups. Some may look at the name of the  
author organization and the "importance" score of the event, and know  
the meaning of that scale of importance. Others may look at the "Why"  
section where the author has a hypothesis ("80% chance it is a  
supernova"). Others may know the meanings of the Group names and  
Param names in the "What" section and be able to decide based on  
these values.

Roy Williams


California Institute of Technology
626 395 3670

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