/*
 * Copyright (c) 2010 Mysema Ltd.
 * All rights reserved.
 * 
 */
package com.mysema.rdfbean.annotations;

import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;

import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import com.mysema.rdfbean.model.IDType;

/**
 * Identifier property. Identifiers can be of three different types: LOCAL, URI
 * or RESOURCE. @Id is required for all updatable classes. There can be only
 * one identifier property per class (hierarchy). Actual type of the identifier
 * property depends on IDType:
 * <dl>
 * <dt>LOCAL</dt>
 * <dd>String or LID</dd>
 * <dt>URI</dt>
 * <dd>String, ID or UID - expecting that all instances are identified by URI</dd>
 * <dt>RESOURCE</dt>
 * <dd>ID</dd>
 * </dl>
 * 
 * For example
 * 
 * <pre>
 * @Id
 * private String id;
 * </pre>
 * 
 * @see IDType
 * @author sasa
 */
@Documented
@Target({ METHOD, FIELD })
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface Id {
    /**
     * @return
     */
    IDType value() default IDType.RESOURCE;

    /**
     * Namespace of the mapped ids. When ns is not empty local names will be
     * bound.
     */
    String ns() default "";
}