Putting the pieces together...

[Ivo Busko]

Doug Tody wrote:
<snip>
> Ivo - regarding your point about data quality vectors:  As you know,
> the SSA data model has a data quality vector.  We don't really know what
> to put in it though.  I don't think we should put anything instrumental
> in nature in the general SSA data model (this can be done but it would
> go into nonstandard extension records).  Simple models for the quality
> vector would be binary (good or bad) or trinary (known good, known bad
> or flagged, or questionable).  Perhaps once we get more experience with
> real data from archives it will be possible to develop a more refined
> quality model.  (Note this should not be confused with the error vectors
> which we already have).
> 
>         - Doug

Thanks, Doug, that sounds good enough. I agree that nothing
instrument-specific
should be put in the data model. However, something must be done to
accomodate
cases that do not follow the norm.

I have in mind cases where a binary or trinary model wouldn't be enough
to summarize the data quality information available in the original
file. 
A good example is FUSE data; it uses a continuously variable 2-byte
integer
value to store a kind of "weight" (between 0 an 100), instead of the
more
commonly found bit-encoded mask. To cast that data into a, say, binary
good/bad
model, one needs an additional piece of information, in the form of a
threshold
value. 

Ideally, a VO transaction involving such data should allow for the
threshold
value to be either specified by the requestor, or alternatively be set
by the
data provider in a instrument-dependent way. 

In short, my point is: shouldn't the data model allow some room for
non-standard
extra bits of info such as data quality threshold values?

Cheers,

-Ivo