Facilitating navigation through commercial spaces by third party systems is a likely step in pervasive computing. For these applications to fully engage people they must build trust relationships in a natural manner. We hypothesize that the use of an explicit trust model in the design of the application would improve the rate at which trust is generated. To investigate this hypothesis, we have taken as a case study the design of a shopping guide for a local trading association.We have created an explicit trust model and incorporated this into our design.We have evaluated both our model and our application. The results of this confirmed our hypothesis and provided additional insight into how to model trust in the design of applications.