A geographic feature can be represented by one or more
data items; for example, the data items in a row of a table.
A data item is the value or values that occupy a cell of
a relational table. For example, consider office buildings and residences.
In the following figure, each row of the BRANCHES table represents
a branch office of a bank. Similarly, each row of the CUSTOMERS table,
taken as a whole, represents a customer of the bank. However, a subset
of each row—specifically, the data items that constitute a customer's
address—represent the customer's residence.Figure 1. Data that represents geographic features. The BRANCHES table contains the columns ID, NAME, ADDRESS, CITY, POSTAL CODE, STATE_PROV, and COUNTRY. The CUSTOMERS table contains the columns ID, LAST NAME, FIRST NAME, ADDRESS, CITY, POSTAL CODE, STATE_PROV, COUNTRY, CHECKING, and SAVINGS. The names and addresses in both tables are fictional.
The tables in this figure contain data that identifies and describes
the bank's branches and customers. This discussion refers to such
data as business data.
A subset of the business data—the values that denote
the branches' and customers' addresses—can be translated into values
from which spatial information is generated. For example, as shown
in Figure 1, one branch office's
address is 92467 Airzone Blvd., San Jose, CA 95141, USA. A customer's
address is 9 Concourt Circle, San Jose, CA 95141, USA. IBM® Spatial Support for Db2 for z/OS® can construct
a ST_POINT column object by using the geocoded x and y coordinate
values. The next figure shows the BRANCHES and CUSTOMERS tables with
new columns that are designated to contain such values.Figure 2. Tables with spatial columns added. In each table, the LOCATION column will contain coordinates
that correspond to the addresses.
Because spatial information will be derived from the data items
stored in the LOCATION column, these data items are referred to in
this discussion as spatial data.
