On 15/12/11 17:25, Paolo Castagna wrote:
Hi Andy,
thanks for the quick reply.
Andy Seaborne wrote:
ARQ has it's own evaluation engine. Currently, it needs code changes to
extend it. It covers most of XSD already.
I had a look into NodeValue.java [1], would it be possible to do something
along these lines?
See NodeValue.compareAlways (which has the SPARQL rules for ORDER BY
which are more than just "<")
Index: src/main/java/com/hp/hpl/jena/sparql/expr/NodeValue.java
===================================================================
--- src/main/java/com/hp/hpl/jena/sparql/expr/NodeValue.java (revision
1214849)
+++ src/main/java/com/hp/hpl/jena/sparql/expr/NodeValue.java (working copy)
@@ -1036,6 +1036,14 @@
boolean b = ((Boolean)lit.getValue()).booleanValue() ;
return new NodeValueBoolean(b, node) ;
}
+
+
+ Object clazz = lit.getDatatype().getJavaClass();
+ if ( clazz.getClass().isInstance(Double.class) )
+ {
+ double d = ((Number)lit.getValue()).doubleValue() ;
+ return new NodeValueDouble(d, node) ;
+ }
That makes it a double, a number, no units.
(aside from the fact doubles are NOT numbers in XSD - use xsd:decimal -
their value space is "m × 2^e" i.e. (m,e) pairs, for fixed length m and
e extended with NaN, Inf, -Inf and a lot of machinery for comparison and
addition etc for rounding and mapping ).
Saying a temperature has a value which is a number is wrong. Different
value spaces.
Can you compare the height of a mountain with a temperature? Ones in
meters, the other in Kelvin.
// If wired into the TypeMapper via
RomanNumeralDatatype.enableAsFirstClassDatatype
// if ( RomanNumeralDatatype.get().isValidLiteral(lit) )
Note that RomanNumeralDatatype are another way to write integers. Same
value space.
Creating an ordering function that returns a number (no units) means
comparison is defined.
[1]
https://svn.apache.org/repos/asf/incubator/jena/Jena2/ARQ/trunk/src/main/java/com/hp/hpl/jena/sparql/expr/NodeValue.java
