Which design pattern aids in creating a clear contract for service interaction?

The correct choice emphasizes the importance of defining a clear contract for service interactions, which is essential in software architecture, especially in service-oriented architectures. The Interface pattern is specifically designed to provide a means by which different components can communicate with one another while adhering to defined contracts.

These interfaces define public methods and properties that a service must implement, allowing for flexibility and encapsulation. By using the Interface pattern, a developer can ensure that different services meet certain standards when they interact with each other. This clear contractual agreement reduces the complexity of dependencies between services and promotes maintainability as services can evolve independently as long as they adhere to the established interface.

In contrast, the other design patterns listed serve different purposes. The Decorator pattern is more about enhancing or extending an object's behavior dynamically, the Builder pattern is focused on constructing complex objects step by step, and the Strategy pattern involves selecting an algorithm's behavior at runtime. None of these patterns inherently provide the clarity and structure needed for defining service contracts as effectively as the Interface pattern does.