The purpose of visualization is not just to depict data, but to gain or present insight into the domain represented in data. However in visualization systems, this link between features in the data and the meaning of those features is often missing or implicit. It is assumed that the user, through looking at the output, will close the loop between representation and insight. An alternative is to view visualization tools as interfaces between data and insight, and to enrich this interface with capabilities linked to users' conceptual models of the data. Preliminary work has been carried out to develop such an interface as a modular component that can be installed in a pipelined architecture. This poster expands the motivation for this work, and describes the initial implementation carried out within the Visualization Toolkit (VTK). CR Categories: I.3.8 [Computer Graphics]: Applications; I.3.m [Computer Graphics]: Miscellaneous;