I try to write a persistent unit in Ruleset I wrote public class Ruleset implements Serializable { ... @OneToMany(cascade={ PERSIST, REMOVE }) @OrderBy ("number ASC") private List<Rule> rules; my Class Rule looks like public class Rule implements Serializable { ... private BigDecimal number; during deployment I get the above error message. I tried remove the @OrderBy anotation. but the error still remains. even when I change the Order to "id asc" (id is a valid property of both classes). when I changed the Order to "ddddddd ASC", i got the above error message for the property Ruleset.ddddddd. when I changed back to "id asc" the error changed back to Ruleset.number what does it mean?