Different results with bnodes depending on the rule order

[eyusupov]

@prefix : <http://example.com/>.

:a :a :b.
:b :b :c.

{ ?a ?a ?b. :a :a :b } => { _:e _:e _:e }.
{ ?b ?b ?c. :b :b :c } => { _:e _:f _:f }.

gives:

eye --quiet --nope --pass-only-new tests/n3/bnodes/bnode-several-rules-same-production.n3
EYE v10.7.2 (2024-05-06)
SWI-Prolog version 9.2.4
starting 71 [msec cputime] 68 [msec walltime]

_:sk_0 _:sk_0 _:sk_0.

While

@prefix : <http://example.com/>.

:a :a :b.
:b :b :c.

{ ?b ?b ?c. :b :b :c } => { _:e _:f _:f }.
{ ?a ?a ?b. :a :a :b } => { _:e _:e _:e }.

gives:

eye --quiet --nope --pass-only-new tests/n3/bnodes/bnode-several-rules-same-production-3.n3
EYE v10.7.2 (2024-05-06)
SWI-Prolog version 9.2.4
starting 75 [msec cputime] 72 [msec walltime]

_:sk_1 _:sk_0 _:sk_0.
_:sk_2 _:sk_2 _:sk_2.