Certification union for Vendor.certified: a boolean flag, a bounded decimal rating, a letter-grade string,
or a gYear.
Spans the full §5.7.5 processing-type ladder (xsd:boolean < numeric < xsd:string < temporal); the grade
pattern keeps the string variant lexically disjoint from the gYear variant, so every value singles out
exactly one branch (§5.4).
Certification union for
Vendor.certified: a boolean flag, a bounded decimal rating, a letter-grade string, or a gYear.Spans the full §5.7.5 processing-type ladder (
xsd:boolean< numeric <xsd:string< temporal); the grade pattern keeps the string variant lexically disjoint from the gYear variant, so every value singles out exactly one branch (§5.4).