The winestore entity-relationship model
Figure 3-3 shows the completed entity-relationship model for the online winestore derived from the system requirements listed in Chapter 1. Appendix C includes a description of the meaning of each shape and line type used in the figure.
Figure 3-3. The winestore ER model
The winestore model can be summarized as follows:
A customer at the online winestore purchases wines by placing one or more orders.
Each customer has exactly one set of user details.
Each order contains one or more items.
Each item is for a specific
quantityof wine at a specific
A wine is of a
typesuch as "Red," "White," or "Sparkling."
A wine has a vintage
year; if the same wine has two or more vintages from different years, these are treated as two or more separate, distinct wines.
Each wine is made by one winery.
Each winery is located in one region.
Each wine has one or more grape_variety entries. For example, a wine of
wine_name"Archibald" might be made of the grape_variety entries "Sauvignon" and "Cabernet." The order of the entries is important. For example, a "Cabernet Sauvignon" is different from a "Sauvignon Cabernet."
Each wine may have one or more inventories.
Each inventory for a wine represents the on-hand stock of a wine that is available at a particular
case_cost(a case is 12 bottles of wine). If a wine is available at two prices, there are two inventories.