Because the mission and vision are key to describing the function and purpose of the company, changing or updating them should be kept to a minimum or under certain circumstances. For example, if the mission and vision are not working, because they were written too narrow or broad, then they should be altered. Another situation for change might be a massive change in the core competency of the company. For example, if Google decided to switch from search engines to application selling as its primary market focus, then this would dictate changing the mission and vision of the company. The mission and vision might also be changed if the company has achieved them. If the vision of a company is to be the largest seller of retail goods in the world and they achieve this end; then they may need to update their vision in order to maintain their motivation and goals. Because the vision and mission are key to explaining the direction and goals of the company, there are few instances in which the should be changed.