An organisation should be able to list the users it has, and the needs of those users that it strives to meet.
To understand the total activity of an organisation, the only thing necessary is to enumerate all of the needs.
This idea extends to the services that are provided. Each service accomodates a set of user needs. By understanding the needs of the user, each service can identify the most appropriate way of measuring the success or fitness of a service.
The Government Digital Service's Service Manual entry on user needs is a good place to start learning about user needs, and how they use them.
The components of a user need
The service manual's example user need is a good example of a need that might be captured in a service contract:
As a British person
I need to provide proof of my identity and visa permissions to border control
So that I can travel abroad and prove my identity
The need captures who has the need (the user), what they need to do (the asset or activity), and why they need to do it (the outcome).
This user need is a particularly good example, because it doesn't make assumptions about how (a passport).
Outcomes & Service Metrics
Outcomes are encapsulated in the why part of a user need, and service metrics should be related the outcome.
Often finding a good way to measure a particular outcome is challenging. From the example above, it might be hard to become immediately aware if someone was unable to prove their identity abroad. However, as long as the executive can agree, a proxy measure can be used as a substitute for a direct measure.
In this case, it could be whether or not someone attempted to travel abroad having used the service.
Often when considering the needs a service strives to meet, people get confused with requirements. The service-level user needs captured in a service contract are often very different from the requirements a service may have for use.
Services may need particular user inputs to achieve the outcomes the user is looking for, and those needs may be expressed in story form, but that should remain a distinct concept from the needs of the user encapsulated in a service contract.