
detselect queries the detrend database to select the best currently
available detrend image matching the supplied criteria.  Detselect has
two major modes, search and select:

** detselect -search 

detselect -search will examine the detrend database and return the
entry detID+iteration which matches the request criteria.  The criteria include:

camera
detrend type

These criteria are required for all 'detselect -search' invocations.
Detselect should exit with an error state if these search criteria are
not included.

Other criteria include:

date/time
filter
exptime
detector temperature
airmass
label

detselect should use the following rules to select the best detrend
data for each query:

* camera must match exactly
* detrend type must match exactly

for the remaining, if the value is supplied:

* date/time must be > date_start and < date_stop
* filter must match exactly (string match)
* exptime must be > exptime_min and < exptime_max
* airmass must be > airmass_min and < airmass_max
* detector temperature must be > det_temp_min and < det_temp_max
* label must match exactly

if the above rules result is more than a single valid detrun, the one
with the greatest value for date_create should be chosen.

if the above rules do not match any detrun, then detselect must return
the value NONE for the det_id.

the output for a successful operation (including the empty set) should
include:

det_id, iteration, class, 


** detselect -select -detID (det_id) -iter (iter) -classID (class_id)

returns the specific master detrend imfile filename which matches the
specified det_id, iteration, and class_id.  the output from this
operation should consist of a single filename, which should have the
value NONE if no match is found.  

** detrend DB tables

The detrend DB tables may be missing some fields needed to perform the
operations above.  these may perhaps be placed in detRun when the
detRun is defined.  here is the list of fields:

date_start  : start of the validity range for the detrend data
date_stop   : end of the validity range for the detrend data

date_create : date when the detrend data was defined (perhaps this
should be the date that the iteration was set, and should be stored in
detRunSummary).

filter       : filter name used to create this data
det_temp_min : minimum valid detector temperature for this data set
det_temp_max : maximum valid detector temperature for this data set
airmass_min  : minimum valid airmass for this data set
airmass_max  : minimum valid airmass for this data set
exptime_min  : minimum valid exptime for this data set
exptime_max  : minimum valid exptime for this data set
label        : a string label used to distinguish related detrend frames 

these values should be specified when creating the detrun, and are
optional (the dettools should not enforce the requirements for
specific detrend types).



