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Logic Modeling. Learning Objectives. Use Structured English as a tool for representing steps in logical processes in data flow diagrams Use decision tables and decision trees to represent the logic of choice in conditional statements
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Learning Objectives • Use Structured English as a tool for representing steps in logical processes in data flow diagrams • Use decision tables and decision trees to represent the logic of choice in conditional statements • Select among Structured English, decision tables, and decision trees for representing processing logic
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
Logic Modeling • Deliverables and Outcomes • Structured English • Decision Tables • Decision Trees • State-transition diagrams • Sequence diagrams • Activity diagrams
Deciding Among Structured English, Decision Tables and Decision Trees
Practical Considerations • Know all 3 techniques. • If you only know how to use a hammer, every problem looks like a nail. • Structured English may be best when • The logic is very simple • The goal is to communicate with users • Decision Tables may be best when • The sequence of the decision criteria (the questions you would ask) is not important • Consistency, completeness and flexibility/scalability are important • You want to depict a large amount of data in a small amount of space • Decision Trees may be best when • The sequence of the decision criteria is important.
Summary • Several methods of logic modeling • Structured English • Primarily communication technique for analysts and users • Decision Tables • Conditions are listed in condition stubs • Possible actions are listed in action stubs • Rules link conditions with actions • Lists all possible rules • Decision Trees • Conditions are portrayed by decision points • Values are represented by paths between decision points and ovals that contain actions
Summary • Comparison of Structured English, Decision Tables and Decision Trees • Most studies show that decision trees are best for many criteria • There is no best technique • Analyst must be proficient in all three