On Thu, 25 Mar 2004, Anita Richards wrote:
> > 1) VOX:Image_Scale --> instr.scale
> >
> > A much better alternative could be the definition of the new ucd1+:
> > obs.image.scale
>
> That still suggest to me that the scale is inherant to the observations -
> but it is better
This is a general issue with what we are calling the "observation" data model. This may be just a naming issue but I worry that we may try to describe actual observations.
What we really need to do for VO is characterize the physical attributes of a dataset. A dataset may be a calibrated observation, or it may be the result of an arbitrary amount of processing of multiple observations, or it may be synthetic data. It does not matter how the dataset was generated if we describe only the physical attributes of the actual final dataset we are dealing with. Scale and resolution are good examples of such physical attributes.
For VO data analysis where we may need to deal uniformly with data from many origins, physical dataset characterization is what is needed. At this level we should not have any information about the actual observations, instrument characteristics, etc., (if any) used to produce the dataset. Such information may be present in each individual dataset, and can be useful to fully understand individual datasets, but is not very useful for automated processing of data from many origins.
A simple example is exposure time. While a typical attribute of an individual original observation, it tells us almost nothing about an arbitrary dataset. To understand what this means we would have to understand the full instrumental model and configuration, and all the post-processing done to get to the final dataset we are actually looking at. The related physical dataset attributes are the sampling and coverage in time of the final (possibly aggregate) dataset, and some physical measure of the limiting flux of a signal detected by the dataset. Received on 2004-03-25Z17:49:22