I heard SHACL helps with specifying structure (shape), and more so than OWL which is more about meaning (and where it may be acceptable to have an incomplete but "open" specification).

Programming with these structures (triple/quad with shape constraints) would be interesting, general-purpose programs could not easily take advantage in the form of static type-checking. This is roughly the same type of problem as the "object-relational impedance mismatch." I believe some kind of type-checking (shape-checking?) for SPARQL queries might be possible, but don't know if any such thing is implemented.