Fig. 7.3.5 A simple dis.The anchor or primary data are indicated by the box of data that is at the top left of the
diagram. The anchor box indicates that the data that relate directly to the key of the box
are description, unit of measure, unit manufacturing cost, packaged size, and packaged
weight. The elements of data exist once and only once for each product.
Data that can occur multiple times are shown beneath the anchor box of data. One such
grouping of data is component id. There can exist multiple components for each product.
Another grouping of data that is independent of component id is inventory date and
location. The product may have been inventoried in multiple places on different dates.
The lines going to the right of the anchor box indicate types of data. In this case, a
product may be used in flight or in ground support.
The dis indicates the keys, attributes, and relationships for an entity.
Chapter 7.3: Data Modeling for the Structured Environment