This paper describes the role that interpretation plays in facilitating situated design and presents an implementation that demonstrates a system interpreting floor plans. Designers often see more in what they produce than they intentionally put there. Cognitive studies suggest that this helps develop design ideas. Interpretation is described as the use of expectations to construct an internal representation of an external representation (such as a sketch). An implementation of this notion of interpretation is described. As an example of its capability the system, primed on floor plans, looks at a randomly generated image and can find a floor plan within it. The system produces different results with the same image if it has different expectations. This is used to discuss the notions of a space of possible designs and the two-way relationship between expectations informing interpretation and interpretation changing the expectations (design ideas) of a designer. Further work is suggested and the ideas are discussed.