Identifies why this milestone exists, what problem it is solving, and/ or what object cannot be modeled using the regular hierarchy.
Best Practice: Although not required by the Tag Set, this should be treated as a required attribute and a value always provided when milestones are used.
Used on Elements: <milestone-end>, <milestone-start>
|Text, numbers, or special characters||The reason for a milestone or information about an object that cannot be modeled using the regular hierarchy.|
|Restriction||@rationale is an optional attribute; there is no default.|