/**
 * Represents an identity of something that is responsible for causing a state change.
 * An identity can be a user, a system, a service or anything else that can be identified.
 */
export declare class Identity {
    readonly subject: string;
    readonly name: string;
    readonly userName: string;
    readonly onBehalfOf?: Identity | undefined;
    /**
     * The identity used when not set.
     */
    static readonly notSet: Identity;
    /**
     * The identity used when the identity is not known.
     */
    static readonly unknown: Identity;
    /**
     * The identity used when the system is the cause.
     */
    static readonly system: Identity;
    /**
     * Initializes a new instance of the {@link Identity} class.
     * @param subject - The identifier of the identity, referred to as subject.
     * @param name - Name of the identity.
     * @param userName - Optional username, defaults to empty string.
     * @param onBehalfOf - Optional behalf of {@link Identity}.
     */
    constructor(subject: string, name: string, userName?: string, onBehalfOf?: Identity | undefined);
    /**
     * Returns a new {@link Identity} chain with duplicate subjects removed.
     * The first occurrence of each subject is kept.
     * @returns A new {@link Identity} with duplicates removed from the chain.
     */
    withoutDuplicates(): Identity;
}
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