Accuracy and semantics in shape-interrogation applications

This paper describes two important questions of semantics, in the context of accuracy in shape interrogation. The first of these questions is how to give meaning to an internally inconsistent solid description based on the widely used trimmed-surface boundary representation. The second question is the meaning of a request, made to a numerical method, to find a solution to a problem whose parameter values are uncertain. Answers to these questions are given, inspired in the case of the second question by a now-standard approach in numerical analysis.