description:
A code distinguishing whether an Act is conceived of as a factual statement or in
some other manner as a command, possibility, goal, etc.
Constraints: An Act-instance must have one and only one moodCode value.
The moodCode of a single Act-instance never changes. Mood is not state.
To describe the progression of a business activity from defined to planned to executed,
etc. one must instantiate different Act-instances in the different moods and link
them using ActRelationship of general type "sequel". (See ActRelationship.type.)