I received feedback in my YANG doctor review (thanks Mahesh) regarding the use 
of decimal64 for most of the values in the geo location grouping 
(https://tools.ietf.org/html/draft-ietf-netmod-geo-location-04). In my 
comparison sections I note that some precision (at the very extremes) may be 
lost when converting from other geo location formats that use string (or double 
for w3c) to decimal64. Given that mention of loss of extreme precision, the 
reviewer was asking if some justification for the decimal64 should be given in 
the document.

What are the advantages to using decimal64 for floating point numbers vs using 
a string with a pattern "[0-9]+(\.[0-9]+)?" (convert that to yang pattern 
language). The advantage of using a string is that the precision of the value 
is not restricted by the model. Does the YANG decimal64 values have a concise 
binary format that can be more efficiently transported or stored in binary 
form? If so is this the only advantage, and is it enough of one to limit the 
precision in the model?

It's definitely worth noting that the precision of the decimal64 values seem 
vastly adequate for geo location data (e.g., for Cartesian coordinates and 
height values which are measured in meters the fractional digits is 6 which 
means the surface could be up to 9 billion kilometers large (or away from for 
height) and the precision is to the micrometer. For ellipsoidal coordinates 
there are 12 fractional digits for the degrees.

Thanks,
Chris.

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