The design of mobile and wearable computing devices involves decisions about how the user interacts with the hardware and software composing the device. Since applications of, and usage environments for, mobile and wearable computers has varied greatly, it has been difficult to build on previously collected design knowledge. The Interaction Constraints Model described in this paper offers an application-neutral and domain-independent approach for comparing different applications and usage scenarios. The Interaction Constraints Model provides a means to map information about user interface implementations to specific work situations. In this way, a system designer can use a set of generic interaction constraints to identify and retrieve information about user interface components from previous projects. In a proof-ofconcept implementation of the Interaction Constraints Model, we were able to validate the approach of the model and we demonstrate the usefulness for the design of wearable computer user interactions.