Requirement: properties.identifier

An identifier is an unlimited-length character sequence that must begin with a Java identifier start character; all following characters must be Java identifier part characters. An identifier start character is any character for which the method Character.isJavaIdentifierStart returns true. An identifier part character is any character for which the method Character.isJavaIdentifierPart returns true.

See:

• Section 3.8.1.1, Message Selector Syntax