System Analysis and Design
System Analysis
- Mr. Ahmad Al-Ghoul
Learning Objectives
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Use decision trees to analyze and
describe processes
Choose appropriate process
specification Analysis Technique
Describe the relationship between
logical and physical models
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Process Description Tools
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Decision Trees
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Graphical representation of the conditions,
actions, and rules found in a decision table
Whether to use a decision table or tree often
is a matter of personal preference
Employ tree structures which show conditions
and actions within a problem
Decision Tree is read from left to right
Root of tree -> name of process
 branches -> conditions
 Leaves -> actions to be performed
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Process Description Tools
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Drawing Decision Trees
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First, identify all conditions and actions and
their order and timing (if they are critical).
Second, begin building the tree from left to
right while making sure you are complete in
listing all possible alternatives before moving
over to the right.
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Process Description Tools [1]
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This decision tree is based on the sales promotion policy
described above $
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Process Description Tools
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Decision Tree Advantages
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The order of checking conditions and executing
actions is immediately noticeable.
Conditions and actions of decision trees are found on
some branches but not on others. Those conditions
and actions that are critical are connected directly to
other conditions and actions, whereas those
conditions that do not matter are absent
Compared to decision tables, decision trees are more
readily understood by others in the organization.
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Selecting a process specification
Analysis Technique
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Use these guidelines:
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Use structured English when there are many
repetitious actions or when communication to
end users is important
Use decision tables when complex
combination of conditions, actions, and rules
are found or you require a method that
effectively avoids impossible situations,
redundancies, and contradictions
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Selecting a process specification
Analysis Technique
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Use decision trees when the sequence of
conditions and actions is critical or when not
every condition is relevant to every action
(the branches are different)
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Logical Versus Physical Models
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Sequence of Models
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Many systems analysts create a physical
model of the current system and then develop
a logical model of the current system before
tackling a logical model of the new system
Performing that extra step allows them to
understand the current system better
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Logical Versus Physical Models
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Four-Model Approach
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Develop a physical model of the current
system, a logical model of the current system,
a logical model of the new system, and a
physical model of the new system
The only disadvantage of the four-model
approach is the added time and cost
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Sequence Summary
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Decision trees consisting of nodes and branches
Decision trees are appropriate when actions
must be accomplished on a certain sequence
There is no requirement that the tree be
symmetrical, so only those conditions and
actions that are critical to the decisions at hand
are found on a particular branch
Structured analysis tools can be used to develop
a logical model during one systems analysis
phase, and a physical model during the systems
design phase
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Sequence Summary
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In this Sequence we have
 Defined and explained decision trees
 Explained where to use decision trees
 Explained how to draw decision trees
 Described the advantages of decision trees
 Explained the guidelines to select a process
specification analysis technique
 explained the relationship between logical and
physical models
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Reference
[1] System Analysis and Design, Sixth Edition
Authors: Gary B. Shelly, Thomas J. Cashman and Harry J. Rosenblatt ,
Publisher: SHELLY CASHMAN SEWIES.
[2] system analysis and design, sixth edition
Authors: Kenneth E. Kendall and Julie E. Kendall
Publisher: Prentice Hall
[3] Modern Systems Analysis and Design Third Edition
Authors: Jeffrey A. Hoffer , Joey F. George, Joseph S. Valacich
Publisher: prentice hall
[4] System Analysis and Design, 3rd Edition
Authors: Dennis, Wixom, & Roth
Publisher: John Wiley & sons
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