Define a vision for the world
A vision is the definite future an institution is willing to judge every small decision against.
Defining a mission
The mission is this institution's role inside the vision, not a sentence that could belong to anyone else.
Once the vision is fixed, the mission is the part of it this institution will actually carry. Not the whole future. Its role.
That role comes from heritage. Two institutions can want the same world and still have different missions, because they were built by different people, in different places, for different work. A mission that could be lifted onto a competitor without anyone noticing is not a mission. It is a category.
The mission is allowed to change. The vision is not a cage around today's products. If the work that once served the vision no longer does, the mission is rewritten and the vision stays. What does not change is the obligation. The mission exists to move the world toward the vision, not to protect the institution from having to change.
Write it so a stranger could tell what you will do, and what you will leave to someone else. A mission with no edge is a wish that the whole organization is the hero of.