The order of evaluation of a message selector is from left to right within precedence level. Parenthesis can be used to change this order. An identifier is an unlimited length sequence of Java letters and Java digits, the first of which must be a Java letter. A letter is any character for which the method Character.isJavaLetter returns true. A letter or digit is any character for which the method Character.isJavaLetterOrDigit returns true.
Identifiers are either header field references or property references.
Identifiers are case sensitive. Message header field references are restricted to JMSDeliveryMode, JMSPriority, JMSMessageID, JMSTimestamp, JMSCorrelationID, and JMSType. JMSMessageID, JMSTimestamp, JMSCorrelationID, and JMSType values may be null and if so are treated as a NULL value. Any name beginning with 'JMSX' is a JMS defined property name. Any name that does not begin with 'JMS' is an application-specific property name.