Service classification revisited
You have learned in the previous chapter that services can be divided into elementary services, composite services, and process services:
Elementary services: The smallest possible components that qualify as services. For example, a service that can be used for zip code lookups.
Composite services: Services that result from combining two or more other services into one service that provides more value. Composite services are executed in a single transaction and their execution time is relatively short. An example is a service to book a hotel and flight together.
Process services: Longer running services that can take a couple of hours, days, or even more to complete and span multiple transactions. An example is a service for ordering a book online. The entire process (order, pay, ship, deliver) involves multiple transactions and takes a couple of hours at least.
The following figure shows this classification of different services:
