The Data Model Resource Book, Volume 3: Universal Patterns for Data Modeling

Silverston c05.tex V2 - 11/21/2008 3:04am Page 202

202 Chapter 5 ■ Types and Categories: the Classification of Data

at multiple levels. For example, it wants to roll up all lower level types such

as ‘‘Processors,’’ ‘‘Storage Devices,’’ ‘‘Business Applications Software,’’ and so

on, into higher level types such as ‘‘Hardware,’’ ‘‘Software,’’ or ‘‘Accessory.’’

This allows senior management to answer questions such as ‘‘What were last

year’s sales for my hardware products?’’ or ‘‘What are next year’s forecasted

sales for storage devices as a percentage of all hardware sales?’’

In Figure 5-5 and Table 5-2 you see three different hierarchies of PRODUCT

TYPE(s) where you can classify HARDWARE products as ‘‘Processors’’ or

‘‘Storage Devices’’; classify SOFTWARE products as ‘‘Business Application

Software’’ or ‘‘Gaming Software’’; or classify ACCESSORY(s) into ‘‘Cases’’

or ‘‘Mouse Pads.’’ In other words, this pattern supports the organization of

classifications into these types of hierarchies or aggregations.

9

Table 5-2 Examples of Hierarchy of Types

PRODUCT TYPE. PRODUCT TYPE. PRODUCT TYPE. PRODUCT TYPE.

PRODUCT TYPE NAME (CHILD) PARENT NAME

ID (CHILD) PRODUCT TYPE ID (PARENT)

10 Processors 1 Hardware

13 Storage Devices 1 Hardware

14 Business Application

Software

2Software

16 Gaming Software 2 Software

12 Cases 4 Accessory

17 Mouse Pads 4 Accessory

1 Hardware 100 Product Type

2 Software 100 Product Type

4 Accessory ...