competing goals for EXISTS solutoins

I see multiple goals for a solution for EXISTS.

1/ The solution should be well-defined, e.g., no operation should be
invoked outside of its defined domain.

2/ The solution should be defined on all SPARQL queries that are currently
syntactically legal.

3/ The solution should be simple, i.e., no complex extra machinery.

4/ The solution should conform to the notions defined for the SPARQL syntax and
the SPARQL algebra, e.g., variable scope should matter.

5/ The solution should conform to the non-normative desires epressed in the
SPARQL document, e.g., bottom-up evaultion of sub-queries should be
possible.

6/ The solution should conform to what SPARQL implementations do.


All of the above goals are problematic except perhaps the first.  They can't
all be satisfied at the same time.  Some of them can't even be satisfied
individually.

I don't see consensus on which of these goals are more important than the
others.

Peter F. Patel-Schneider
Nuance Communications

Received on Saturday, 25 March 2017 18:15:18 UTC