/**
 * Type of a URL subject.
 */
export type IUrlSubject = {
    type: 'url';
    url: string;
};
/**
 * Type of an attribute subject.
 */
export type IAttributeSubject = {
    type: 'attribute';
    attribute: string;
};
/**
 * Type of a value subject.
 */
export type IValueSubject = {
    type: 'value';
    value: any;
};
export type IPointerSubject = {
    type: 'pointer';
    pointer: string;
};
/**
 * Type of a reference subject.
 */
export type IReferenceSubject = IUrlSubject | IAttributeSubject | IValueSubject | IPointerSubject;
/**
 * A reference points to an external resource.
 * References can be used in middleware DSLs to refer
 * to a URL, or to an attribute of a document.
 */
export interface IReference<T extends IReferenceSubject> {
    /**
     * The reference subject.
     */
    subject: T;
}