In this section, the DDL definitions that describe the properties
of categories, category groups, and subcategories are presented.
Figure 
illustrates the schema for these categories.
Figure:
The schema of DDL definitions that describe categories, subcategories,
and category Groups.
In this figure, boxes surround data items which belong to the
same category. Category identifiers are given in large font
and item names are given in small font. Parent-child relationships
are specified by lines connecting data items with the arrow pointing
at the parent item. Key items within a category are identified
by a preceding black dot.