[JENA-1943] Increase Precision of Decimal Calculation Results

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 3.14.0, Jena 3.16.0
• Fix Version/s: Jena 3.17.0
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Jan Martin Keil
• Created: 14/Aug/20 13:45
• Updated: 01/Dec/20 14:31
• Resolved: 16/Aug/20 21:41

Description

The precision of calculation results with type xsd:decimal is limited without need.

An Example:

import org.apache.jena.query.QueryExecutionFactory;
import org.apache.jena.rdf.model.ModelFactory;
import org.junit.jupiter.api.Test;

public class MaxDecimalDivissionPrecissionTest {

	@Test
	public void maxDecimalDivissionPrecission() {
		String query = "PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> "//
				+ "SELECT"//
				+ "  (     STR(1/STRDT(\"1000000000000000000000000\", xsd:decimal)) AS ?times10)"//
				+ "  (     STR(1/STRDT(\"10000000000000000000000000\", xsd:decimal)) AS ?calculated)"//
				+ "  (DATATYPE(1/STRDT(\"10000000000000000000000000\", xsd:decimal)) AS ?type)"//
				+ "  (     STR(  STRDT(\"0.0000000000000000000000001\", xsd:decimal)) AS ?direct)"//
				+ "  (     STR(1/STRDT(\"0.0000000000000000000000000000000000000000000001\", xsd:decimal)) AS ?large)"//
				+ "WHERE {}";
		System.out.println(QueryExecutionFactory.create(query, ModelFactory.createDefaultModel()).execSelect().next().toString().replace(" (", "\n("));
	}
}

Output:

( ?times10 = "0.000000000000000000000001" )
( ?direct = "0.0000000000000000000000001" )
( ?calculated = "0.0" )
( ?large = "10000000000000000000000000000000000000000000000.0" )
( ?type = xsd:decimal )

 
I would expect ?calculated == ?direct. This only affects very small numbers, very large numbers are not affected. I also checked Wikibase and RDF4J and did not find this limitation. Please consider to remove this limitation as I need higher precision in a view cases in a project.