Information assurance
Information assurance is the act of working with business and IT leadership to ensure that the confidentiality, integrity, and availability requirements for a given asset are fully understood. Those requirements should be fully tested in a test environment prior to being integrated into the production environment, in order to ensure that they are secure and do not cause interoperability issues.
The activities associated with information assurance inform the activities associated with IT security regarding the specific technical controls needed to properly protect a given asset. Requirements are driven by the business/mission owner.
For example, a medical device might be deemed by a business/mission owner to be confidentiality-high, integrity-high, and availability-moderate (because they can revert to old school medical techniques):
Relationship between Information Assurance and IT Security