[JENA-817] SUM(?a) {empty} is error but SUM( DISTINCT?a) {empty} is value zero.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 2.12.1
• Fix Version/s: Jena 2.13.0
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 24/Nov/14 11:21
• Updated: 02/Dec/14 11:42
• Resolved: 02/Dec/14 11:42

Description

They can't both be right!

The fix is to make sum(empty) zero. Looks like the code use to do that but was left is a debugging state.

In SQL, sum(empty) is NULL.

In SPARQL 1.1, sec 18.5.1.3:
Sum(S) = "0"^^xsd:integer when card[S] = 0
so it is zero.