The validation framework already conforms to the OpenAPIKit idiom: named
composable Validation values, a Validator with blank/validating/
withoutValidating, located errors, parameterized over both subject and
document. The DTD layer is already four named rules.
XSD content validation stays a single recursive Validation
(contentValidity) rather than a rule per constraint, because XSD is a
recursive type system: a child's type is resolved from its parent's
content model and position, then rewritten by xsi:type and the derivation
controls mid-walk, so the constraint categories are interdependent and
cannot be split into independent rules without changing semantics or
duplicating the recursion. That is the sanctioned multi-error form.
To keep each category verifiable on its own (the idiom's testability),
add XSDCategoryTests exercising ComplexValidator directly per category
(attributes, content, nillable, fixed); derivation, wildcards, and
namespaces are already isolation-tested through crafted schema strings.
Closes#101
Mihaela Mihaljevic
50a6afb3fc