I think we have decimal all wrong ...

After todays meeting I tried out several XQuery processors and could not find any that would produce -0 for a decimal.
"-0E0 cast as xs:decimal" returns 0


Thinking this is a bug or maybe a "MAY" instead of "MUST" 
I reread the xsd specs again

http://www.w3.org/TR/xmlschema-2/#decimal

>From close reading I interpret that the value space of decimal can NOT include -0

" The ·value space· of decimal is the set of numbers that can be obtained by multiplying an integer by a non-positive power of ten, i.e., expressible as i × 10^-n where i and n are integers and n >= 0."

There is no way to get a -0 from this to my reading. (even though the prior sentence says "decimal represents a subset of the real numbers, which can be represented by decimal numerals." ... the further refinement of the next sentance is fairly clear).

so mathematicaly, decimal is a subset of real, but not including -0.
Or so I interpret.

Now the lexical representation can have a -0  ... but it should not be treated different from 0 same as the example given with precision.   
" the number 2.0 is not distinct from the number 2.00. "


>From this I am forced to conclude that it is an artifact of EXI codec specifications, not a fundamental mathematical principal or based on XSD specs that decimal needs to represent -0.

So I suggest any warning we write only go on to state, if anything, that this is a EXI specific representation issue and not suggest there is any other reason for it.


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David Lee
Lead Engineer
MarkLogic Corporation
dlee@marklogic.com
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