Organizes business logic by procedures where each procedure handles a single request from the presentation.

—Martin Fowler1

A system’s public interface can be seen as a collection of business transactions that consumers can execute, as shown in Figure 5-1. These transactions can retrieve infor‐ mation managed by the system, modify it, or both. The pattern organizes the system’s business logic based on procedures, where each procedure implements an operation that is executed by the system’s consumer via its public interface. In effect, the sys‐ tem’s public operations are used as encapsulation boundaries.

1 Fowler, M. (2002). Patterns of Enterprise Application Architecture. Boston: Addison-Wesley.

Figure 5-1. Transaction script interface