SHACL syntax and metamodel complexity

SHACL states property constraints in the following way

  for the fillers of property ex:p
  the special fillers must all belong to class ex:s,
  there must be at least one,
  there must be at least five special fillers,
  they must all be either ex:a, ex:b, ex:c, ex:d, ex:e, ex:f, ex:d, ex:h,
    ex:i, or ex:j,
  there must be at most ten,
  the identifiers used for them must match regular expression r,
  they must all belong to class ex:c, and
  there must be at most seven special fillers.

but not in the following way

  for the fillers of property ex:p
  there must be at least one,
  they must all belong to class ex:c,
  there must be at most five,
  they must all belong to class ex:d, and
  there must be at least three.

In my opinion, these features of the SHACL RDF syntax are contributing to
the complexity of the SHACL metamodel and to the number of decisions that
have to be made to construct the SHACL metamodel.


If SHACL stated constraints in the following way

  there must be at least one filler of property ex:p,
  all the fillers of property ex:p must belong to class ex:c,
  there must be at most five fillers of property ex:p,
  all the fillers of property ex:p must belong to class ex:d, and
  there must be at least three fillers of property ex:p.

then the the metamodel for SHACL constraints could have just particular
constraints (from the clauses above and other constraint constructs).  This
would be a significant simplification of the metamodel.


Even if SHACL permitted the second construction above and uniformly stated
multi-part particular constraints as at the end of the following there might
be significant simplifications of the metamodel

  for the fillers of property ex:p
  there must be at least one,
  they must all be either ex:a, ex:b, ex:c, ex:d, ex:e, ex:f, ex:d, ex:h,
    ex:i, or ex:j,
  there must be at most ten,
  the identifiers used for them must match regular expression r,
  they must all belong to class ex:c, and
  there must be at between five and seven fillers that belong to class ex:s.


These simplifications would require changes to the RDF syntax of SHACL.

peter

Received on Wednesday, 24 February 2016 17:04:29 UTC