$Id: README,v 1.5 1999/05/13 03:09:52 dbyrne Exp $

About  UPDATING DATASETS:
The MANIFEST, a list of datasets available through the browser, is 
automatically re-generated each time you update the browser.  It is 
a list of the files necessary for the browser to find and download
datasets over the Web.

The first entry on each line of the manifest is the name of the 
'archive.m' file for that dataset  -- an archive.m file is simply a 
Matlab script with some metadata about a particular dataset and some 
information about how and where it is stored.

For example, the archive.m file for the declouded Hatteras to Nova Scotia 
1.1km resolution AVHRR dataset is called 'htn_decld.m'.  You will find 
this script in the browser subdirectory DATASETS.

When you push one of the 'update dataset' buttons, the browser downloads 
a new MANIFEST file, and reads each line.  If the item read is the first 
one on the line, the browser assumes it is an archive.m file, fetches it 
across the Web, and attempts to parse it.

The dataset ranges, what variables it contains, and the specific Matlab 
function serves as an interface between DODS and the browser (called the 
'getxxx' function) are all contained in the archive.m.

Once the browser has successfully fetched and parsed the archive.m file 
for that dataset, it looks at which getxxx function this dataset must have 
to run.  This information is contained in the archive.m variable 
'GetFunctionName'.  Some datasets share getxxx functions (for example, 
many gridded datasets can use the same getxxx function); if the browser 
does not have that particular getxxx function it fetches it.

Next the browser goes on to look for other arguments on the same line of 
the manifest.  These will be extra routines that are necessary for that 
dataset to be used within the browser -- for example some special scripts 
converting decimal time (e.g., 1997.6324) to year, month and day, and
other things like that.

The browser fetches each of these files in turn, if there are any.

Dataset ranges (geographic, time and depth) the variables they contain, and 
the name of the archive.m and getxxx function for each one are stored 
INTERNALLY in the browser.  That is, it does not check the manifest each 
time you start it up, nor does it check the ranges in the archive.m, EXCEPT 
WHEN UPDATING.  "Update dataset list" is the ONLY way to force those ranges 
to change.  The "ALL" option is the only way to update the ranges of datasets
already in your browser's list.