Creating an object in an object-oriented programming platform

An application programming interface is provided in an object-oriented programming platform for developing applications. A method comprises, in response to a first message received at a first object that contains one or more properties, creating a second object that responds to a second message sent thereto responsive to sending of the first message to the first object and returning the second object. By returning, for example, key-value collection proxies by specific key-value coding methods a read-only or a read-write access may be allowed to a collection of a container object's related objects. A specific implementation of one object's class may change over time without requiring changes in another object's implementation.