Logic Modeling Learning Objectives Use Structured English as

Logic Modeling

Learning Objectives Use Structured English as a tool for representing steps in logical processes in data flow diagrams ü Use decision tables and decision trees to represent the logic of choice in conditional statements ü Select among Structured English, decision tables, and decision trees for representing processing logic ü

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

Logic Modeling Techniques

Deciding Among Structured English, Decision Tables and Decision Trees Criteria Structured English Decision Tables Decision Trees Determining Conditions and Actions 2 nd 3 rd 1 st Transforming Conditions and Actions into Sequence 1 st 3 rd 1 st Checking Consistency and Completeness 3 rd 1 st

Practical Considerations ► Know all 3 techniques. ► Structured English may be best when ► Decision Tables may be best when ► Decision Trees may be best when § If you only know how to use a hammer, every problem looks like a nail. § The logic is very simple § The goal is to communicate with users § 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 § The sequence of the decision criteria is important.

Summary ► Several methods of § Structured English ► Primarily logic modeling 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