Person Lookup Proposal

/**
 * Searches for a single {@link IPersonAttributes} using the specified uid (userName).<br>
 * 
 * This method returns according to the following rules:<br>
 * <ul>
 *  <li>If the user exists and has attributes a populated {@link IPersonAttributes} is returned.</li>
 *  <li>If the user exists and has no attributes an {@link IPersonAttributes} with an empty attributes Map is returned.</li>
 *  <li>If the user doesn't exist <code>null</code> is returned.</li>
 *  <li>If an error occurs while find the person an appropriate exception will be thrown.</li>
 * </ul>
 * 
 * @param uid The userName of the person to find.
 * @return The populated {@link IPersonAttributes} for the specified uid, null if no person could be found for the uid. 
 * @throws IllegalArgumentException If <code>uid</code> is <code>null.</code>
 */
public IPersonAttributes getPerson(String uid);

/**
 * Searches for {@link IPersonAttributes}s that match the set of attributes provided in the query {@link Map}. Each
 * implementation is free to define what qualifies as a 'match' is on its own. The provided query Map contains
 * String attribute names and single values which may be null.
 * <br>
 * If the implementation can not execute its query for an expected reason such as not enough information in the
 * query {@link Map} null should be returned. For unexpected problems throw an exception.
 * 
 * @param query A {@link Map} of name/value pair attributes to use in searching for {@link IPersonAttributes}s
 * @return A {@link Set} of {@link IPersonAttributes}s that match the query {@link Map}. If no matches are found an empty {@link Set} is returned. If the query could not be run null is returned.
 * @throws IllegalArgumentException If <code>query</code> is <code>null.</code>
 */
public Set<IPersonAttributes> getPeople(Map<String, Object> query);

/**
 * Searches for {@link IPersonAttributes}s that match the set of attributes provided in the query {@link Map}. Each
 * implementation is free to define what qualifies as a 'match' is on its own. The provided query Map contains
 * String attribute names and single values which may be null.
 * <br>
 * If the implementation can not execute its query for an expected reason such as not enough information in the
 * query {@link Map} null should be returned. For unexpected problems throw an exception.
 * 
 * @param query A {@link Map} of name/value pair attributes to use in searching for {@link IPersonAttributes}s
 * @return A {@link Set} of {@link IPersonAttributes}s that match the query {@link Map}. If no matches are found an empty {@link Set} is returned. If the query could not be run null is returned.
 * @throws IllegalArgumentException If <code>query</code> is <code>null.</code>
 */
public Set<IPersonAttributes> getPeopleWithMultivaluedAttributes(Map<String, List<Object>> query);