Database Reference
In-Depth Information
“1.1 Get Name.” he term
1.1 Get Name
will also appear in a process dic-
tionary that will contain a detailed specification for how to program this
procedure.
Other modeling tools include:
Entity relationship diagram
: An ERD is a database model that describes
the attributes of entities and the relationships among them. An entity
is a file (table). Today, ER models are often created graphically, and
software converts the graphical representations of the tables into the
SQL code required to create the data structures in the database, as
shown in Figure 7.4.
State transition diagram
: A STD describes how a system behaves as a
result of external events. In Figure 7.5, we see the effects of a person
reporting a pothole.
Data dictionary
: The data dictionary is a very organized listing of all
data elements that pertain to the system. This listing contains some
very specific information, as shown in Figure 7.6. It should be noted
that there are many variations in the formats of data dictionaries.
New Data Entered
Store Data
Reading Citizen
Input
Request Repair Crew
New Pothole ID Saved
Process Pothole Work Order
Store Pothole
Information
Repair Crew
Input
Assign Available Crew
Pothole Work Order
Complete
Store Work Order by
Pothole ID
Create Pothole
Work Order
Request Repair Crew
Cost Input
Calculate Crew Cost
New Pothole ID
Create Pothole Damage File
Damage File Complete
Store Damage File by Pothole ID
Request Repair Crew
Cost Input
Calculate Damage Cost
Create Pothole
Damage File
FIGURE 7.5
State transition diagram (STD).
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