The second of the two representations I have developed describes object shape in terms of the boundary of the object. This representation provides the four basic shape description mechanisms introduced at the start of the previous section in the following ways:
This shape representation does not make any use of axes, and it provides no space filling information of the type that is provided by the subparts or imples of the ASSF representation. The information which it does contain is in fact mostly a subset of the ASSF representation - a description of the shape boundary can be constructed using the types of qualitative shape feature described as part of the ASSF representation. As a subset, the basic shape representation of the EPB technique is therefore simpler, but less intuitively obvious to humans than the hierachy of subparts and features.