In a software project, as in any large project, a significant amount of work is needed to close the project. Teams often defer the hard issues of finally delivering a product until much too late in the process, leading to trouble when the time finally arrives.

This chapter examines the ENVY notion of prerequisites in depth, sees how it can affect packaging, and looks at resolving various prerequisite problems. We will look at various alternatives for the packaging and delivery process and their relative advantages and disadvantages. We'll describe in some detail the packaging and delivery process for both VisualAge and VisualWorks. We'll look at application attachments, an ENVY mechanism for keeping track of external files associated with our program. Finally, we'll address some additional delivery issues and strategies for ensuring that packaging does not become a bottleneck.

Prerequisites Revisited

Before we examine program delivery strategies, it's worth revisiting some of the concepts we've previously seen that have a significant effect on delivery. Regardless of our strategy, knowing what other code our program relies on is important if we are to produce a simple, standalone program. Recall that ENVY provides the notion of application prerequisites to help formalize this information. Some packaging strategies, particularly those using the VisualAge packager, rely heavily on correct prerequisites to determine which components need to be linked and which classes and methods can be discarded. Even if we're not using such a mechanism, ENVY prerequisites can help define a layered architecture with all the dependencies made clear.