CIS 321—IS Analysis & Design
Chapter 6: The Traditional
Approach to Requirements
Traditional vs. OO
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This chapter focuses on what the system does when
an _______ occurs: activities and interactions.
This chapter follows the traditional approach.
The traditional approach to systems involves
processes, stored data, inputs, and ________.
The OO approach to systems involves a collection of
interacting objects with attributes and __________.
See diagram on p. 201 for comparisons.
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Data Flow Diagrams (DFD)
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DFD’s are very common in the traditional approach.
DFD: A graphical ______ that shows requirements
for inputs, outputs, processes and data storage.
Five symbols
Item inquiry
Catalog
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process
data flow
external agent
data store
real-time link
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Customer
Look up
item
availability
Item availability
details
Product item
Inventory item
This diagram corresponds to
the first event on p. 168. and
the data entities on p. 180
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Context Diagrams
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DFD’s can show high-level or low-level processing
(levels of ____________).
A single process in a higher level DFD can be
decomposed into an entirely new DFD at a lower
level.
A ________ diagram shows the complete view of a
system at the highest level of abstraction.
A context diagram would only show data stores
shared with other systems.
A context diagram can be created from an event
table.
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Diagram 0
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A DFD __________ is created for each event in the
event table.
All DFD fragments are drawn after the event table
and the context diagram are complete.
All the DFD fragments can be combined in a single
DFD called the ______-partitioned system model or
diagram 0.
Diagram 0 shows the entire system in greater detail
than the context diagram.
Diagram 0 may be too complex for large systems.
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Logical and Physical DFD’s
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A logical DFD assumes perfect technology with no
specific technology implementations.
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perfect technology implies no ______ checking
this models the way things should ideally be done
a logical DFD is best for ______ analysis
A physical DFD contains some technology
implementations.
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hardware, data files, user interface, manual processes
this may model the way things are done now
a physical DFD is best for late analysis or early _______
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DFD Quality
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Minimize complexity
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avoid information __________
keep chunks of information to 7 +/- 2
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processes in a DFD
data flows entering or leaving a process
Ensure data flow consistency
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balancing
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______ hole
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data flow at a higher level DFD should match those at the lower
level
data entering a process are not needed
miracle
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data leaving a process have insufficient sources
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Documentation of DFD
Components
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Process descriptions
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process decomposed in a lower level DFD
eventually, a process must be defined
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Data dictionary
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Data flow definitions
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structured ________ (similar to pseudocode, preferred, p. 219)
decision tables and decision trees for complex logic (p. 221)
lists all the data elements (_______) in the flow
corresponds to attributes of data entities in the ERD
Data store definitions (s/b included in ERD)
Data element definitions (data types, length of strings, …)
DFD Summary
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Information Engineering Models
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In the early 1980’s SD and ID were competitors.
IE SDLC
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SD vs. IE
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Systems planning (focus on __________ and stored data)
Business area analysis (focus on each business area)
System design (describe processes in detail)
System construction (using _______ tools)
IE focuses on the entire enterprise, SD does not
IE phases are tightly coupled, SD more moderately so
IE models
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process decomposition diagram (p. 229)
process dependency diagram (p. 230)
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Locations and Networks
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Where will processing and data stores be located?
This information may be useful in analysis to
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A location diagram summarizes locations (p. 232)
The activity-location matrix (p. 233)
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generate and evaluate _____________
review recommendations with management
lists event table __________ in rows
lists locations in columns
The activity-data matrix (p. 234)
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lists event table activities in rows
lists data stores in columns
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