In this chapter, you learned to identify what services you need before you dive into their design. Services are identified in a top-down fashion when they are derived from an overall strategy or plan, which is usually formalized in a to-be architecture and roadmap. Such a roadmap dictates what services to create, when, and in what order. Bottom-up service identification occurs when you investigate your existing IT assets, and derive services from there. This chapter explains why meet in the middle is the best approach.
This chapter also discussed what makes a good or a poor service based on design principles such as isolation and idempotency. Most important is that services need to be easy to use, must provide value, and that they can be trusted by (future) consumers.
As we have seen, not all services have the same relevance and we need to categorize services since different principles and guidelines apply to different types of services. The next chapter continues to explore such classification...