On Wednesday 13 August 2003 4:20 pm, Roy Williams wrote:
> > As far as I can
> > tell, all efforts so far to define a dictionary of complete and unique
> > terms have failed because it's very difficult.
>
> Or maybe impossible? Can we really imagine defining science words in such a
> close and accurate way that they can be compared by a computer, yet the
> community of astronomers will agree to it? Does the word "planet" include
> Pluto? What exactly does the word "image" mean?
Even if it's impossible we still need to do it :-) otherwise we will not be able to do the joins and comparisons that we want to, nor carry out the kind of automatic registry searches that we intend to. We don't have to define all words; we 'just' have to define terms that describe certain data values that apply to the astronomy world. (I see possible cause of confusion: 'Complete' here meant that the term(s) must describe the value completely, rather than all things must be described). Certainly we must be careful about trying to find a Universal Solution that is so generic and vague that it is very difficult to use in practice.
The data modelling team are working on describing data values, which is useful for data servers. This forum probably needs to look at (if it's not done already!) how it will describe metadata in the registry using terms that software can interpret. How, for example, will we say that a particular data set contains intensities in absolute ergs, while another contains the same information but in magnitudes? Similarly with passband filters, pixel resolutions, data quality, etc, etc.
-- Martin Hill Astrogrid/AVO, ROE Tel: 07901 55 24 66Received on 2003-08-13Z17:43:57