Extend arbitrary length property path to return only furthest node

[jaw111]

Why?

When querying tree-like structures, it is often useful to find the leaves of an arbitrary length path.

In some case it is possible to do this using MINUS or FILTER NOT EXISTS to remove solutions:

:john foaf:knows+ ?leaf .
MINUS { ?leaf foaf:knows [] }

However for more complex traversals where the arbitrary length match is part of a larger sequence it can be hard to formulate.

Previous work

unknown

Proposed solution

Allow use of some modifier like ~ that will exclude the intermediate nodes along that path segment.

:john foaf:knows+~ ?leaf .

In case the graph contains cyclical, then stop traversed when finding an already visited node and give no result for that traversal.

Considerations for backward compatibility

None foreseen