I have trying to make a strongly type GP system to generate search queries.  The terminals are integers which point to a set of 200 words.  Internal functions take String arguments and produce a Boolean query which will return a specific set of documents (which determines the fitness):

e.g. (word7 OR (word9 AND word200))
My question is what is the best way to specify the terminal set  - do I need to specify a node for every integer terminal or is there an equivalent of the GA min-gene /max gene approach?