Generates a SPARQL OPTIONAL group pattern.
OPTIONAL
Wraps the clauses in an optional group. Empty clauses, such as those produced by nil, are dropped first; when none survives, the result is the empty fragment via nil, which callers must guard against where a matching pattern is required.
optional
The graph pattern clauses to wrap
The SPARQL OPTIONAL group pattern, or the empty fragment for no clauses
SPARQL 1.1 Optional Patterns
Generates a SPARQL
OPTIONALgroup pattern.Wraps the clauses in an
optionalgroup. Empty clauses, such as those produced by nil, are dropped first; when none survives, the result is the empty fragment via nil, which callers must guard against where a matching pattern is required.