RE: [oic] "Principled Assessment" applied to YEARFRAC

["Dennis E. Hamilton" <dennis.hamilton@acm.org>]

I see that I need to make clear that the first principled inspection is this:

1. I would want to make some simple calculations for every basis and where the start date is December 31 and the end date is January 1 *of* *the* *next* *year*.  That is, the interval is exactly one day.  (I am assuming that when the start and end date are the same for YEARFRAC, the answer should be 0.  That should be confirmed first, I suppose.)

 - Dennis
 

-----Original Message-----
From: Dennis E. Hamilton [mailto:dennis.hamilton@acm.org] 
<http://lists.oasis-open.org/archives/oic/201003/msg00003.html>
Sent: Monday, March 01, 2010 08:31
To: oic@lists.oasis-open.org
Subject: [oic] "Principled Assessment" applied to YEARFRAC

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APPLICATION TO YEARFRAC

Here is how I would build an assessment for the handling of YEARFRAC in all of the places where it shows up directly and indirectly.

1. I would want to make some simple calculations for every basis and where the start date is December 31 and the end date is January 1.  The cases should include December 31 for leap years, January 1 for leap years, and cases where neither is in a leap year.  This simple test reveals a number of conditions:

   a. Which year the single day in the span December 31 is assumed to be in
   b. How many days that year is assumed to have (by computing 1/YEARFRAC(December31date;January1date)
   c. How precisely the one-day fraction is determined (might take more work)

2. I would be interested in simple cases for exact whole year intervals, both from December 31 to the December 31 one year later (with the usual leap-year variations), and also from January 1 to January 1 one year later (ditto).  These are supposed to be exactly one in all of the YEARFRAC cases I am aware of.

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6. One value of a principled assessment is that it has two valuable outcomes:

  a. It grounds what OpenFormula specifies for the result, where an implementation offers reliable coverage, and where the OpenFormula provisions are out of reach.

  b. It reveals to users, experts, and other interested parties whether the OpenFormula definition for a function meets their expectation or whether they need to consider how to adjust their use of OpenFormula functions (such as YEARFRAC) in order to obtain the result they need while being able to count on how OpenFormula is specific.

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