Logic Modeling

1. Logic Modeling Represents the internal structure and functionality of the processes represented on data flow diagrams

2. Structured English A modified form of the English language used to specify the logic of information systems processes

3. Structured English versus Pseudocode • Structured English resembles spoken English • Structured English uses a subset of the English vocabulary to express information system process procedures • Pseudocode resembles a programming language

4. Sequence, Conditional, Repetition Mimics indentation format utilized in programming languages Does not include Variable initialization Open/close of files Logic for matching files Communication Tool for analysts and users Sequence, Conditional and Repetition Initializes Variables Opens/closes files Requires logic for matching files Communication tool used for programmers and analysts Structured English versus Pseudocode Structured English Pseudocode

5. Structured English • Three Processes Of Structured Programming • Sequence • Conditional Statements (Decision) • IF • CASE • Repetition • DO UNTIL • DO WHILE

6. Structured English IF Statement BEGIN IF If Quantity in stock is less than reorder point THEN GENERATE Order END IF

7. Structured English Case Statement SELECT CASE Case 1 (Grade is A) Multiply credit by 4 to get grade points Case 2 (Grade is B) Multiply credit by 3 to get grade points Case 3 (Grade is C) Multiply credit by 2 to get grade points Case 4 (Grade is D) Assign credit to grade points All other cases grade points = 0 END CASE

8. Structured English DO UNTIL DO READ next Inventory Record BEGIN IF If Quantity in stock is less than reorder point THEN GENERATE Order END IF UNTIL end of file (Inventory)

9. Structured English DO WHILE READ first inventory record WHILE NOT end of file DO BEGIN IF IF quantity in stock is less than reorder point THEN GENERATE new order END IF READ next inventory record END DO

10. Structured English • Uses action verbs to describe processes • Uses nouns to describe data structures • Fields on a data file • Contains no adjectives or Adverbs

11. Logical DFD - Ketler’s Version Decomposition of Process 1.0 1.1 Update Inventory Added Supplier Inventory D1 Products Qty Added 1.2 Update Inventory Used Amounts Used Stock on Hand Counts

12. Logical DFDActivities 3 and 4: Generate orders & pay order 3.0 Generate Orders Supplier Inventory D1 Orders Qty on hand Reorder qty Reorder point Invoice payment 4.0 Pay Bill

13. Logical DFD - Ketler’s Version 1.0 Update Inventory Added Supplier Products Inventory D1 Qty Added payment Invoice 2.0 Update Inventory Used Amounts Used Stock on Hand Counts Inventory 3.0 Generate Orders D1 Qty on hand Reorder qty Reorder point Orders 4.0 Pay Bill

14. Structured English for Process 1.0 Update Inventory Added DO READ next invoice-item-record (info from supplier) Find matching inventory-record Add Quantity from invoice item record to quantity in stock on inventory-record UNTIL end of file (invoice-item from supplier)

15. Structured English for Process 2.0 Update Inventory Used DO READ next Stock-item-record (from stock list) FIND matching inventory-record SUBTRACT Quantity-used from Stock-item-record from quantity in stock on inventory-record UNTIL end of file (stock list)

16. Structured English for Process 3.0 Generate Orders DO READ next Inventory Record BEGIN IF If Quantity in stock is less than reorder point THEN GENERATE Order END IF UNTIL end of file (Inventory)

17. Structured English for Process 4.0 Generate Payments READ Today’s Date DO SORT invoice records (from supplier) by Date READ next Invoice record (from supplier) BEGIN IF If Date is 30 days or greater than Today’s Date THEN GENERATE Payments END IF UNTIL end of file (Invoice – from supplier)