| PREVIOUS | CONTENTS | FORWARD |
A sub-group represents the lowest level of an interpreted assemblage of contexts. A context can only belong to one sub-group. While for instance an excavation record (context 101) can contain a numbered lens (context 102), a sub-group cannot incorporate another sub-group. Sub-groups are sets of closely related contexts of human activities, which will later be linked into groups.
Sub-groups contain stratigraphically closely related contexts that form part of the same 'process' or in other words, of the same processual 'small phase' event such as construction, use (of the surface), or disuse and/or abandonment. From the finds' point of view, makeup often contains more residual than contemporary material, whereas occupation debris and the lower levels of destruction material in situ provide the most contemporary items. Therefore, as shown in Table 13, it is not vitally important for the sequence if the elements of construction and use (of a surface) or use and disuse cannot be separated, as contexts of either of these two processual phases may also be joined into one sub-group under an appropriate heading. Construction and use could also continue as alteration, resurfacing or repair of the same room. If several resurfacings can be distinguished they should form new sub-groups because they help to divide a time span.
The same rule applies for timber and masonry structures: one sub-group contains all closely related stratigraphic components of a building phase, whereas separate elements of repair and disuse form new sub-groups.