Unexpected behaviour from backward chaining rules, for blank nodes and query variables

[renyuneyun]

Observation 1

Backward chaining rules whose conclusion contains new query variables (that do not exist in premise) result in reasoner error: ** ERROR ** gre ** error(permission_error(modify,static_procedure,(,)/2),context(system:assertz/1,_210)).

Example:

@prefix : <http://example.org/ns/>.

:Alice a :Human.

{
	?m a :World;
		:has ?h.
} <= {
	?h a :Human.
}.

Observation 2

Backward chaining rules whose conclusion contains blank nodes seems to do nothing.

Example:

@prefix : <http://example.org/ns/>.

:Alice a :Human.

{
	_:m :has ?h.
} <= {
	?h a :Human.
}.

{ 
	?a :has ?b.
} => {
	?a :has ?b.
}.

The example in #35 also does not work.