Github user afs commented on the issue:
https://github.com/apache/jena/pull/299
Executing SPARQL over the id-specific standard RDF representation of RDF*,
could be done with without needing to modify the core algebra by expansion of
`<<:s :p :o>>` in BGPs.
For `BIND(<<:s :p :o>> AS ?t)` (from earlier work - it has gone now?) it
can be done with a custom function `:findTriple(:s :p :o)` to return the
reification bnode but it must be a single match (a good reason for not having
or restricting it to ground s/p/o.).
With that, I think an extension can go in a separate maven module as a pure
extension.
(This is by thinking about it, not coding it.)
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