1. In a computing environment, a method of creating an application as a composite part comprising a plurality of interconnected parts including a business logic part, a user interface part, and one or more connectors for connecting the user interface part to the business logic part, the composite part enabling a developer to create a business logic part that implements desired business logic functionality and another developer to create a user interface part that implements a user interface design independently of one another, the method comprising: creating a business logic part that defines two or more commands that the business logic part is designed to execute; creating, within the business logic part, a connection point for each of the two or more commands that defines an internal interface through which the business logic part exposes the corresponding command to enable the corresponding command to be invoked by another part; creating a user interface part that defines one or more user interface components to be displayed within a user interface; creating, within the user interface part, a connection point, for each of the one or more user interface components, that defines an external interface through which the corresponding user interface component invokes one of the one or more commands defined in the business logic part when the user interface part is connected to the business logic part; and creating, for each connection point in the user interface part, a connector that connects the corresponding connection point of the user interface part to a connection point of the business logic part, the connector comprising adaptor code that includes a first interface for interfacing with the external interface of the corresponding connection point defined within the user interface part and a second interface for interfacing with the internal interface of the corresponding connection point defined within the business logic part, the first and second interface adapting communications between the external and internal interfaces to thereby allow the command exposed by the corresponding connection point of the business logic part to be invoked when the corresponding user interface component is selected in the user interface; creating a second user interface part that defines one or more user interface components to be displayed within a user interface; creating, within the second user interface part, a connection point, for each of the one or more user interface components, that defines an external interface through which the corresponding user interface component invokes one of the one or more commands defined in the business logic part when the second user interface part is connected to the business logic part; and replacing the user interface part with the second user interface part by creating, for each connection point in the second user interface part, a connector comprising adaptor code that includes a first interface for interfacing with the external interface of the corresponding connection point defined within the second user interface part and a second interface for interfacing with the internal interface of the corresponding connection point defined within the business logic part, the first and second interface adapting communications between the external and internal interfaces to thereby allow the command exposed by the corresponding connection point of the business logic to be invoked when the corresponding user interface component is selected such that the second user interface part can be plugged into the composite part without modifying the business logic part by using the connector for each connection point in the second user interface part to adapt to each connection point in the business logic part to thereby enable the second user interface part to be plugged in to the composite part without modifying the business logic part.