Thinking in Promises

Chapter 7. Service Engineering

It will not come as a surprise that there is a simple connection between the concepts of promises and services. Promises are valuable to other agents when kept reliably, or at last predictably, and they can even be sold or traded. This is the basis of a service.

Service buoys the human experience, on a day-to-day basis. There are dumb services, like web servers and directory service lookups, or ATM cash-point transactions, where we don’t expect or even want too much intelligence, but there are also experiential services like hotels and restaurants where humans are directly involved, and the subtle semantics are everything to the assessment of the outcome.

Services make up a potentially complex topic because they are a meeting place between the key ingredients of promises: semantics, dynamics, and valuation.

• Services have to work in detail (semantics).

• Services have to operate at some scale (dynamics).

• Services have to be economically viable to survive (economics).

In this chapter, I want to sketch out a few of these issues. The real power of Promise Theory comes from a more formal, symbolic toolset, but that is the subject of a different book.

Promise Theory makes a simple prediction about services, which is possibly counterintuitive. It tells us that the responsibility for getting service ultimately lies with the client, not the server. That clarifies a few things about the design of systems where services play a role.

The Client-Server ...