export interface ExtensionReferenceValidateResult {
    ok: boolean;
    category: string;
}
export interface ExtensionReferenceType {
    tag: string;
    attrOrder: readonly string[];
    validate?: (attrs: Record<string, string>) => ExtensionReferenceValidateResult;
}
export declare function registerExtensionReferenceType(spec: ExtensionReferenceType): void;
export declare function getExtensionReferenceType(tag: string): ExtensionReferenceType | undefined;
export declare function listExtensionReferenceTypes(): ExtensionReferenceType[];
export declare function clearExtensionReferenceTypes(): void;
