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30 Part 1 • SyStemS analySiS FundamentalS

Figure 2.12 Patron-name
Patron-address
A more complete E-R diagram, Patron Patron-phone
showing data attributes of the Patron-credit-card
entities.

is in
the makes
name
of

Reservation-number
Patron-name
Reservation
Performance-number
Concert/show
Date
Time
Location
is Price
has made
for

Performance-number
Performance Concert/show
Date
Time
Location
Price-options

has belongs to

Concert/show
Concert/Show Concert-details
Dates-of-event
Location

It is critical that a systems analyst begin to draw E-R diagrams upon entering an organiza-
tion rather than waiting until the database needs to be designed because E-R diagrams help the
analyst understand what business the organization is actually in, determine the size and scope of
the problem, and discern whether the right problem is being addressed. The E-R diagrams need
to be confirmed or revised as the data-gathering process takes place.

Use Case Modeling
Originally introduced as a diagram for use in object-oriented UML, use cases are now being used
regardless of the approach to systems development. A use case diagram can be used as part of the
SDLC or in agile modeling. The word use is pronounced as a noun (“yoos”) rather than a verb
(“yooz”). A use case model describes what a system does without describing how the system
does it; that is, it is a logical model of the system. (Logical and conceptual models will be further
discussed in Chapter 7.) A use case model reflects the view of a system from the perspective of a
user outside the system (that is, the system requirements).