The Stratigraphic Model

For the purposes of the archive it has been assumed that users will wish to analyse rather than edit the data. The context and grouping data describing the archaeological stratigraphy has therefore been presented in a cross-tabulated manner rather than as a sequential list of contexts. 

This model allows finds and environmental sample data to be attached to the stratigraphic model using the fields SiteCode and Deposit. 

For example; all finds for any Phase, Feature, Intervention or deposit can be retrieved by filtering on the required field (Landscape, Feature, Intervention, Deposit).

Higher level interpretations (the archaeological entities and interpretative groups) can be linked to the stratigraphic model. For entities the fields SiteCode and Feature would be used. For interpretative groups, the fields SiteCode and StratigraphicGroup would be employed. This allows the retrieval of all finds or environmental samples for each entity or interpretative group. A diagram demonstrating these approaches can be found in StratigraphicModelDiagram.pdf.

Where appropriate the Stratigraphic Model has been directly incorporated into the Geographic Information shape files

The field descriptions for the model can be found in the file StratigraphicModel_FieldDescriptions.csv. 

Technically, the primary key for the model consists of the fields SiteCode and Deposit. 

The model is constructed so that all deposits are included. Where there are errors in the stratigraphic recording these will be indicated by blank values in Feature and Intervention. For example, if a fill cannot be located within its cut, the field Intervention will be empty. If an intervention cannot be assigned to a feature, the field Feature will be empty. This can be used as an estimate of the accuracy and consistency of the stratigraphic model.

The data in the fields Rank and SGRank are constructed from computer processing of the stratigraphic relationships to provide a numeric value allowing deposits and stratigraphic groups to be sorted vertically by stratigraphic position within a feature or intervention. The lower the numeric value, the earlier the deposit in the feature. A feature or intervention which has a value for all the deposits within it can be assumed to have a consistent set of stratigraphic relationships. Any blank or empty values within a feature are indicative of problems with the stratigraphic recording or data entry.

Should it be a requirement to reconstruct a sequential list of contexts from this Stratigraphic Model then construct a list of the distinct values from the fields described as "Is a context number" in the column Logical_Data_Type in  StratigraphicModel_FieldDescriptions.csv.

Additional explanatory information about the Framework Archaeology recording methods can be found in Landscape Evolution in the Middle Thames Valley, Heathrow Terminal 5 Excavations Volume 1, Perry Oaks, Framework Archaeology 2006, pp 15-22.