Top-Down Design is a methodology that starts at the highest level of a design concept and proceeds towards the lowest level. You start with the broad project specification in mind and put that information in a centralized location. Then you progress from this information to the individual parts. This makes it easy to design and manage large product assemblies. You can make changes from a central location that will propagate to all levels of the design.
Creo Parametric provides us with very powerful Top-Down Design tools. If implemented properly, multiple design teams and designers can work on a project concurrently and communicate design data easily and quickly, with full confidence that all components will fit seamlessly into the final product.