BPEL has emerged as the de-facto standard for implementing processes based on web services while formal languages like Petri nets have been proposed as an "academic response" allowing for all kinds of analysis. Although languages such as BPEL and Petri nets can be used to describe service flows, they both tend to "overspecify" the process and this does not fit well with the autonomous nature of services. Therefore, we propose DecSerFlow as a Declarative Service Flow Language. By using a more declarative style, there is no need to overspecify service flows. The declarative style also makes DecSerFlow an ideal language for monitoring web services, i.e., using process mining techniques it is possible to check the conformance of service flows by comparing the DecSerFlow specification with reality. This can be used to expose services that do not follow the rules of the game. This is highly relevant given the autonomous nature of services.