[Esip-discovery] proposal for seasonal / annually-repeating-dates

Lynnes, Christopher S. (GSFC-6102) christopher.s.lynnes at nasa.gov
Wed Jul 17 15:08:59 EDT 2013

We find ourselves wanting to search a server for a set of repeating date ranges, to support seasonal analysis.  For example, we want all March data over a 12 year period, say, or all data from Dec. 21 to March 20 over a 10 year period.

I would like to suggest a formulation using the ISO 8601 specification for Recurring time interval (http://en.wikipedia.org/wiki/ISO_8601#Repeating_intervals), e.g., R3/2008-03-01T13:00:00Z/P1Y, which describes a one year duration, repeating 3 times, with each year starting on March 1st, i.e., 

2008-03-01T13:00:00Z to 2009-03-01T12:59:59Z
2009-03-02T13:00:00Z to 2010-03-01T12:59:59Z
2009-03-03T13:00:00Z to 2011-03-01T12:59:59Z

Now in our case, we want discrete sub-intervals within the year, repeating each year. However, we can use the start and end times to encode this. For Mar/Apr/May, we would have:

time:start = R3/2003-03-01/P1Y  (Repeat 3 times, interval duration is 1 year)
time:end = R3/2003-05-31/P1Y

These would expand out to:
Start: 2003-03-01, 2004-03-01, 2005-03-01
End: 2003-05-31, 2004-05-31, 2005-05-31

Giving 3 pairs of start-stop times:
2003-03-01 - 2003-05-31
2004-03-01 - 2004-05-31
2005-03-01 - 2005-05-31

So we would not have to modify the OpenSearch template; just allow additional ISO 8601 specifications of more complicated dates.

Who else would be interested in making use of such a construct?
Dr. Christopher Lynnes     NASA/GSFC, Code 610.2    phone: 301-614-5185
"Making the simple complicated is commonplace; making the complicated simple, awesomely simple, that's creativity." -- C. Mingus

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