On 11/08/2020 06:17, Chavdar Ivanov wrote:
Dear all,
I have a very basic question...
I need to compare literals that are floats and tried to use two ways.
1) using sh:equals to compare 2 properties and 2) using SPARQL where I
filter != different values
For the filter I tried using
FILTER (xsd:float(?value1)!=xsd:float(?value1)).
or
FILTER (?value1!=?value1).
Both give the same outcome.
Below I listed a summary of the tests I did
I think sh:equals treats the literals as strings even though they are
floats. It also gives 2 results. I thing this looks like according to
the SHACL spec although I didn't if the sh:equals ignores the datatype.
sh:equals will compare the RDF nodes, so the datatype will make a big
difference and "1"^^xsd:float will be different from "1"^^xsd:string or
integer.
However In some cases the result form the SPARQL is kind of strange.
It looks like the precision is 10-6, but for the big numbers and when
scientific form on float number is used we have something different.
What is followed to define the difference?
If I use google calculator
100123456.1-100.123459E+06=-2.90000000596
Normally it should be OK to compare different forms of float.
1) using sh:equals in the property shape
Value1 ; value 2 ; comparisson result
1.123456 ; 1.123456 ; same
1.1234560 ; 1.1234561 ; different (sh:equals reports it twice)
31.1234560 ; 31.1234561 ;different (sh:equals reports it twice)
30 ; 30.0000001 ; different (sh:equals reports it twice)
30 ; 30.000001 ; different (sh:equals reports it twice)
100123456.0 ; 100123456.1 ; different (sh:equals reports it twice)
100123456.0 ; 100123456.0 ; same
100123456 ; 100.123456E6 ; different (sh:equals reports it twice)
100123456 ; 100.123456E+06 ; different (sh:equals reports it twice)
-0.123456789 ; -123.456789E-3 ; different (sh:equals reports it twice)
-0.123456789 ; -123.456789E-03 ; different (sh:equals reports it twice)
100123456.1 ; 100.123456E+06 ; different (sh:equals reports it twice)
100123456.1 ; 100.123459E+06 ; different (sh:equals reports it
twice)
100123456.1 ; 100123459 ; different (sh:equals reports it twice)
100123456.1 ; 100123459.0 ; different (sh:equals reports it twice)
2) using SPARQL (in the property shape)
1.123456 ; 1.123456 ; same
1.1234560 ; 1.1234561 ; different
31.1234560 ; 31.1234561 ;different
30 ; 30.0000001 ; same
30 ; 30.000001 ; different
100123456.0 ; 100123456.1 ; same
100123456.0 ; 100123456.0 ; same
100123456 ; 100.123456E6 ; same
100123456 ; 100.123456E+06 ; same
-0.123456789 ; -123.456789E-3 ; same
-0.123456789 ; -123.456789E-03 ; same
100123456.1 ; 100.123456E+06 ; same
100123456.1 ; 100.123459E+06 ; same
100123456.1 ; 100123459 ; same
100123456.1 ; 100123459.0 ; same
In SPARQL you may be better off with xsd:decimal than xsd:float, as
xsd:decimal has more precision. But this is more of a SPARQL/ARQ
question for which you may get more qualified help elsewhere, e.g. on
jena-users.
Holger
Best regards
Chavdar
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