We explore invariants as a linking mechanism between the business and technical service perspectives: From the business perspec- tive, invariants can be used to model (business) requirements of an en- terprise; from the technical perspective, invariants express the properties that must hold during the execution of a service. We propose an approach to enterprise service design that can be de- scribed as an iterative introduction and a modication of invariants in response to the evolution of business and/or technical service specica- tions. We formalize the service specications in Alloy and demonstrate how each design iteration can be simulated, visualized and validated with the Alloy analyzer tool. We illustrate our ndings with the example of Order Creation service.