A top-level xs:attribute declaration (a direct child of schema, or of redefine)
was accepted with use, form, or ref. Those belong to a local attribute use, not
a global declaration: the schema-for-schemas topLevelAttribute marks ref, form,
and use as prohibited, allowing only default, fixed, id, name, type and an inline
simpleType. The per-component applicability table is the permissive global/local
union, so it could not draw the distinction; a focused scan of the direct
attribute children of schema and redefine supplies the global-only constraint. A
local attribute use inside a complex type or attribute group is unaffected.
The existing test_validAttributeValues asserted a top-level attribute with use
compiles, which is itself invalid; corrected to a local attribute use.
XSTS: invalid schemas accepted 454 to 439, no other bucket raised.
