Services express their purpose and capabilities via a service contract. The Standardized Service Contract design principle is perhaps the most fundamental part of service-orientation in that it essentially requires that specific considerations be taken into account when designing a service's public technical interface 
and assessing the nature and quantity of content that will be published as part of a service's official contract.
A great deal of emphasis is placed on specific aspects of contract design, including the manner in which services express functionality, how data types and data models are defined, and how policies are asserted and attached. There is a constant focus on ensuring that service contracts are both optimized, appropriately granular, and standardized to ensure that the endpoints established by services are consistent, reliable, and governable.