There are several possible strategies that could be employed in developing the two levels. One possibility is top-down development. In that case, we ignore the tool issues initially and instead first focus on the global capabilities and infrastructure. This approach would hinder our ability to get tools to the users in a timely manner. Furthermore, some of the consequences of the bottom level (tool) issues on the top level issues may not be understood when the top level is initially developed.
The bottom-up approach has the advantage of getting tools out to the user quickly, but leaves the user with a fragmented set of tools that would be frustrating to use. For example, a user would need to re-enter some data when using more than one tool. We have begun our efforts with the bottom-up approach with the Visual Target Tuner release in June. This was a valuable experience for understanding the tool level issues.
Therefore, our current strategy is work on both levels at the same time. This means that we are not concentrating all resources on providing tools to the user in as short a time as possible. On the other hand, we will gain an understanding of the top level sooner. The key to making it possible to work on both levels in parallel is defining a clean interface (API) between the two levels. The API may require some iteration as development proceeds. In this approach users will get an integrated system earlier than with the bottom-up approach.