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chaPter 8 • analyzing systems Using Data Dictionaries 215

Figure 8.5
Physical elements added to a data
structure.
Customer Billing Statement = Current Date +
Customer Number +
Customer Name +
Address +
5
{Order Line} +
1
(Previous Payment Amount) +
Total Amount Owed +
(Comment)
Order Line =
Order Number +
Order Date +
Order Total

The repeating group notation may have several other formats. If the group repeats a fixed
number of times, that number is placed next to the opening brace, as in 12 {Monthly Sales},
where there are always 12 months in the year. If no number is indicated, the group repeats indef-
initely. An example is a table containing an indefinite number of records, such as Customer
Master Table = {Customer Records}.
The number of entries in repeating groups may also depend on a condition, such as an entry
on the Customer Master Record for each item ordered. This condition could be stored in the data
dictionary as {Items Purchased} 5, where 5 is the number of items.
Data Elements
Each data element should be defined once in the data dictionary and may also be entered previ-
ously on an element description form, such as the one illustrated in Figure 8.6. Characteristics
commonly included on the element description form are the following:

1. Element ID. This optional entry allows the analyst to build automated data dictionary
entries.
2. The name of the element. The name should be descriptive, unique, and based on what the
element is commonly called in most programs or by the major user of the element.
3. Aliases, which are synonyms or other names for the element. Aliases are names used by
different users in different systems. For example, a CUSTOMER NUMBER may also be
called a RECEIVABLE ACCOUNT NUMBER or a CLIENT NUMBER.
4. A short description of the element.
5. Whether the element is base or derived. A base element is one that is initially keyed into
the system, such as a customer name, address, or city. Base elements must be stored in
files. Derived elements are created by processes as the result of a calculation or a series of
decision-making statements.
6. The length of an element. Some elements have standard lengths. In the United States, for
example, lengths for state name abbreviations, zip codes, and telephone numbers are all
standard. For other elements, the lengths may vary, and the analyst and user community
must jointly decide the final length, based on the following considerations:
a. Numeric amount lengths should be determined by figuring the largest number the
amount will probably contain and then allowing reasonable room for expansion.
Lengths designated for totals should be large enough to accommodate the sum of the
numbers accumulated in them.
b. Name and address fields may be given lengths based on the following table. For exam-
ple, a last name field of 11 characters will accommodate 98 percent of the last names in
the United States.
c. For other fields, it is often useful to examine or sample historical data found in the
organization to determine a suitable field length. If the element is too small, the data that
need to be entered will be truncated. The analyst must decide how that will affect the