It is all very well placing an emphasis on analysis. However the digital publication must also fill the gap left by the historical narrative of the monograph and that gap is the record of the historical remains.

In designing the Framework FreeViewer we had therefore to balance making the application more powerful with keeping the application accessible for those simply wanting to consult the record. For accessibility, we concentrated on providing the bare minimum of commands.

There are those allowing movement around the map: zooms, pans; there are those allowing filtering and export of the data to external formats; and those allowing access to descriptions of the features and finds, and the drawings and photographs created in the course of fieldwork. Entry points from the reading of the monograph into the data are provided by pre-defined layers which can be added and removed in the course of interaction with the data and by the ability to search using context, object and sample numbers - all important simply to allow a user to orientate themselves.

Interaction with the data brings its own issues. As author of the software you don't know what layers may already be displayed and how, and adding new layers can bring clashing colour schemes.

Some archaeological features are tiny and it is difficult to ensure these can be seen when loaded. Of course, Google Earth deals with an issue like this by taking you on an elaborate pan and zoom to the location of the added data. For a layer like Fig 2.16 Early Neolithic tree-throws (published in the Perry Oaks data from Heathrow), which are scattered across the entirety of the excavated area at Terminal 5, this would bring little benefit and we settled for fading out existing layers.

This focus on providing a simple, arguably simplistic, interface obviously impacts on the power of the application in conducting an analysis.

As far as analysis goes, we feel that if the application can get you around the data fast enough to allow you a relatively easy familiarisation with the excavation and provoke in the mind some questions then it has done its job. If those questions can be answered using the Framework FreeViewer then all the better, but it is at this point that data is to be  filtered, sorted and exported for examination in more fully featured GIS and database packages of your choice.