Transcript Modern Systems Analysis and Design Ch1

Modern Systems Analysis
and Design
Fifth Edition
Jeffrey A. Hoffer
Joey F. George
Joseph S. Valacich
Chapter 8
Logic Requirements
Learning Objectives
 Use
Structured English as a tool for
representing steps in logical
processes in data flow diagrams.
 Use decision tables to represent the
logic of choice in conditional
statements.
Chapter 8
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Learning Objectives (Cont.)
 Select
among Structured English and
decision tables for representing
processing logic.
 Understand how logic modeling
techniques apply to the development
of electronic commerce applications.
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Logic Modeling
Data flow diagrams do not show the logic
inside the processes.
 Logic modeling involves representing
internal structure and functionality of
processes depicted on a DFD.
 Logic modeling can also be used to show
when processes on a DFD occur.

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Modeling a System’s Logic
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Deliverables and Outcomes
Structured English representation of
process logic.
 Decision Tables representation.
 Sequence diagram.
 Activity diagram.

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Modeling Logic with Structured
English
Structured English: modified form of
English language used to specify the logic
of information system processes.
 No single standard.
 Typically relies on action verbs and noun
phrases and contains no adjectives or No
specific standards.

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Modeling Logic with Structured
English (Cont.)
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Modeling Logic with Structured
English (Cont.)
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Modeling Logic with Decision
Tables
Decision table: a matrix representation of
the logic of a decision which specifies the
possible conditions for the decision and
the resulting actions.
 Best used for complicated decision logic.

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Modeling Logic with Decision
Tables (Cont.)
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Modeling Logic with Decision
Tables (Cont.)
Condition stubs: that part of a decision
table that lists the conditions relevant to
the decision.
 Action stubs: that part of a decision table
that lists the actions that result for a given
set of conditions.

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Modeling Logic with Decision
Tables (Cont.)
Rules: that part of a decision table that
specifies which actions are to be followed
for a given set of condition.
 Indifferent condition: in a decision table,
a condition whose value does not affect
which actions are taken for two or more
rules.

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Modeling Logic with Decision
Tables (Cont.)

Procedure for Creating Decision Tables
 Name
the condition and the values that each
condition can assume.
 Name all possible actions that can occur.
 List all possible rules.
 Define the actions for each rule.
 Simplify the table.
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Modeling Logic with Decision
Tables (Cont.)
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Deciding Among Structured English
and Decision Tables
Criteria
Structured
English
Decision
Tables
Determining
Conditions and
Actions
Second Best
Third Best
Transforming
Conditions and
Actions into
Sequence
Best
Third Best
Checking
Consistency and
Completeness
Third Best
Best
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Electronic Commerce
Application: Logic Modeling
Pine Valley Furniture development
methodology dictated that the logic within
each unique processes be represented.
 Structured English was chosen for
modeling the logic.

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Electronic Commerce Application:
Logic Modeling (Cont.)
Figure 8-8 Level-0 DFD for the WebStore system
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Electronic Commerce Application:
Logic Modeling (Cont.)
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Summary

In this chapter you learned how to:




Chapter 8
Use Structured English as a tool for representing
steps in logical processes in data flow diagrams.
Use decision tables to represent the logic of
choice in conditional statements.
Select among Structured English and decision
tables for representing processing logic.
Understand how logic modeling techniques apply
to the development of electronic commerce
applications.
© 2008 by Prentice Hall
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