extension PureXML.Schema {
    /// The result of compiling a schema document: its global element
    /// declarations, its named-type table, and the identity constraints declared
    /// on each element name.
    struct XSDCompiled {
        var elements: [String: ElementType]
        var types: [String: ElementType]
        var constraints: [String: [IdentityConstraint]]
        /// Simple types for identity-constraint field paths.
        var identityFieldTypes: [String: SimpleType] = [:]
        /// `default`/`fixed` value constraints on identity-constraint field
        /// targets, so an absent attribute or empty element takes that value as its
        /// identity-tuple component.
        var identityFieldConstraints: [String: ValueConstraint] = [:]
        /// Identity fields whose declared target is not a simple type, so the field
        /// violates cvc-identity-constraint.3 (idZ010).
        var identityNonSimpleFields: Set<String> = []
        /// Local names of elements declared `nillable="true"`.
        var nillableElements: Set<String> = []
        /// The `default`/`fixed` value constraint declared on each element name.
        var elementConstraints: [String: ValueConstraint] = [:]
        /// Local names of complex types declared `abstract="true"`. Bare-keyed, for
        /// the schema-consistency rules and direct unit tests.
        var abstractTypes: Set<String> = []
        /// Local names of element declarations declared `abstract="true"`: they may
        /// not appear in an instance directly, only through a substitution member.
        var abstractElements: Set<String> = []
        /// Derivation methods the named type forbids when used through `xsi:type`.
        /// Bare-keyed.
        var typeBlock: [String: Set<DerivationMethod>] = [:]
        /// Derivation methods each element declaration forbids through `xsi:type`.
        /// Bare-keyed.
        var elementBlock: [String: Set<DerivationMethod>] = [:]
        /// Each named complex type's base type and derivation method, the backbone
        /// the schema-consistency rules walk. Bare-keyed.
        var typeDerivation: [String: TypeDerivation] = [:]
        /// Namespaced (`{ns}local`) views of the abstract-type set, `block` tables,
        /// and derivation backbone, for the INSTANCE-validity subsystem, where two
        /// imported types sharing a local name in different namespaces must not
        /// collide.
        var nsAbstractTypes: Set<String> = []
        var nsTypeBlock: [String: Set<DerivationMethod>] = [:]
        var nsElementBlock: [String: Set<DerivationMethod>] = [:]
        var nsTypeDerivation: [String: TypeDerivation] = [:]
        /// Each named union simple type's member type keys (`{ns}local`), so the
        /// `xsi:type`-`block` check can follow a derivation that reaches the
        /// declared union through one of its members (cos-st-derived-OK 2.2.4).
        var nsUnionMembers: [String: [String]] = [:]
        /// Derivation methods each named type declares `final`, for the
        /// schema-consistency rules.
        var typeFinal: [String: Set<DerivationMethod>] = [:]
        /// The schema's target namespace, so the root element's namespace can be
        /// checked against it.
        var targetNamespace: String?
        /// Schema-validity findings gathered while parsing (malformed facet
        /// definitions and the like), reported together with the model-level
        /// consistency findings when the schema is compiled.
        var schemaErrors: [PureXML.Validation.ValidationError] = []
        /// Global attribute declarations keyed by ``attributeDeclarationKey(_:)``.
        var globalAttributes: [String: AttributeUse] = [:]
    }
}