Q class specification of candidate() method

The specification does not clearly specify the behavior of the Q classes in Section "14.10 Typesafe Query Construction"

The examples in section "14.11 Examples" use the following methods of generated Q-classes:

• candidate()
• candidate(String)
• variable(String)

Both candidate methods are used in the query examples, but they are not specified as part of the typesafe query support.

Specific points that we should possibly mention:

• These methods should allow Q classes to be used concurrently. Specifically, they should all return new instances. The current specification allows returning shared multiple instances which causes problems when used concurrently. (the reference implementation currently does this for 'candidate()').
• The reference implementation also has a 'parameter(String)' method. We may want to add this to the spec.