When reading this code, the programmer can focus on the basic functionality and ignore the tuning - in this case, by simply ignoring the TiledParent pragma. An open implementation presents two interfaces. The primary interface provides the functionality and the meta-interface allows the client to adjust the implementation strategy decisions that underlie the primary interface. Achieving this kind of separation has been the focus of much open-implementation research. Although this may sound somewhat esoteric, it is exactly what open implementations need - an interface for controlling the implementation strategy that sits behind the primary interface.
Open implementation is a growing area of interest, and there are many issues to explore.
How to decide what implementation-strategy decisions to expose. Implementation technologies to support open implementation. Finding more examples of existing ad-hoc open implementations and studying them to learn more about the approach. For more information about Open Implementation, see the Site Guide for our web site.