My thought is that if you do not appreciate the function-mission distinction, you probably have your canine anatomy all mixed up. Functions will almost inevitably dominate missions, especially in a pluralistic democracy. But, please don't hang up. Let me explain. Human needs are naturally prioritized.
Some needs are more basic than others.
When these basic needs are threatened, the efforts of the organism are focussed on their satisfaction even if the pursuit of higher needs must be relinquished. We can extend this image of a hierarchy of needs to organizations. Unless basic needs are secure, higher order ones will be relinquished. Functions are those regularly achieved outcomes that address, among other things, the basic survival needs of the organization. Missions are those aspirations which an organization, secure in its survival needs, tends to pursue.