GIS in Historical Research: The North-West Shropshire Tithe Maps and Apportionments



Capturing the Data Digitally

The Entity-Relationship Diagram

Data Normalisation

The Database Table Structure

Working with the Database


The Entity-Relationship Diagram

The first step in designing the database is to construct an entity-relationship diagram. An entity-relationship diagram creates a conceptual model of the data. An entity is an object of interest that we do not wish to further subdivide. Five entities are identified in the data.

The Parish, an administrative unit of the church, is the area for which each tithe return was drawn up. It has attributes of county, valuer (the person who surveyed the land and assigned values to the tithes) and assistant commissioner (the official responsible for approving the apportionment).

Land parcels are the basis of the ownership and occupation of land. Changes over space and time in their ownership and occupation, and in their size and use, indicate changes in social and economic conditions.

Tithe areas are the units for which the tithe charge is calculated. Tithes are of interest as a measure of the productivity of the land. The amount of tithe paid (rent) is solely an attribute of the tithe area. Tithes may be payable to several collectors and in some cases there are two 'types' of tithe, an original amount and a revised amount.

Although for the most part tithe area and land parcel are identical, neither tithe areas nor land parcels are the basic map areas. In some cases tithe areas are subdivisions of a land parcel; in other cases tithe areas are aggregations of land parcels. The mapped areas we term land use areas. These form a distinct entity, with attributes of area, description, land use, parish, township, county, surveyor and commissioner.

Individuals (person) are the social fabric of the area and the economic functionaries. Individuals are related to land parcels and tithe areas through their having an interest in the parcel or area. An interest may be ownership, occupation, or collection of tithes, hence the attribute of type attached to the relationship. The only attributes of individuals recorded in the apportionment are their name and title.

Most relationships are many-to-many (shown on the diagram as M:N); for example, one person can have an interest in many land parcels and one land parcel can have many people interested in it. The relationship between land parcel and parish, and land use area and township is one to many (1:M); e.g. a land use area is in only one parish, but a parish has many land use areas.

The Entity-Relationship diagram for the NW Shropshire Tithe Data