[thredds] Aggregations and Global Attributes

• To: thredds@xxxxxxxxxxxxxxxx
• Subject: [thredds] Aggregations and Global Attributes
• From: Steve Ansari <steve.ansari@xxxxxxxx>
• Date: Wed, 16 May 2012 14:28:32 -0400

Hello Ethan, John, (and list),

We have some global attributes that need some special handling during the
aggregation.  I've looked into promotion of global attributes to variables,
but I'm not sure that is what I want to do here.

I am most interested in:
1) Interpreting the *time_coverage_start , **time_coverage_end *and
*time_coverage_duration
*attributes so they are changed to represent the new actual time coverage
and duration in the aggregation.

2) Rules and operations for how to handle attributes such as date_modified,
date_issued, date created, comment, etc...
   Operations could include:
     a) promoting to variable (if you want to keep track of which time had
which value)
     b) creating an array of unique values
     c) taking the min or max value
     d) taking the first or last value
     e) enforce a single unique value, throwing an error or warning if the
value changes between underlying files as the aggregation is
assembled/cached.

Do these features exist in NcML or the TDS configs somewhere already?

Thanks!
Steve