3/5/2009Computer systems1 Describing Process Specifications and Structured Decisions 1. Process specifications sometimes called mini-specs 2. Structured English 3. Decision tables 4. Decision trees

3/5/2009Computer systems2 Process Specifications Goals: 1. Reducing the ambiguity nof the process 2. Obtaining a precise description n of what is accomplished 3. Validating the system design

3/5/2009Computer systems3 Exceptions Process that n represent physical input or output n represent simple data validation n use prewritten code

3/5/2009Computer systems4 Process Specification Format Process specifications link the process to DFD and hence data dictionary 1. Process number (ID) 2. Process Name 3. Brief description 4. A list of input data flows 5. Output data flows 6. Type of process 7. Names of subprogram or function (code involved) 8. A description of the process logic n that states policy and business rules

3/5/2009Computer systems5 Common Business Rules Common business rule formats: n Definitions of business terms n Business conditions and actions n Data integrity constraints n Mathematical and functional derivations n Logical inferences n Processing sequences n Relationships among facts about the business

3/5/2009Computer systems6 Using Structured English When the process logic involves: n formulas n iteration or repetition n structured decisions are not complex

3/5/2009Computer systems7 Structured English Structured English is based on: n Structured logic n Simple English statements – add – multiply – move

3/5/2009Computer systems8Conventions Types of structures : n Sequential structure n Decision structure – case structure n iteration structure

3/5/2009Computer systems9Example n Sequential structure – formulas or arithmetic calculation n Decision structure – if-then-else – case n Iteration structure – do-loop, do while, do until – for-loop

3/5/2009Computer systems10 Arithmetic Operators n add or + n subtract or - n multiply or * n division or / Example: n X + 2 * Y – Z / 2

3/5/2009Computer systems11 Logical Operators n And n Or n Not Examples: n S and T n W or U n not V

3/5/2009Computer systems12 Decision Tables n 2 by 2 table (four quadrants) n Columns – Conditions and Actions – Rules n Rows – Conditions – Actions

3/5/2009Computer systems13Example Example of decision table 1 Y N X Y 2 Y Y X N 3 N N X Y 4 N Y X N Call supervisor for approval Communicate electronically with bank for credit card authorization Complete the sale. No Signature needed. Complete the sale after verifying signature Under $50 Conditions and Actions Pays by check with two forms of ID Uses credit card

3/5/2009Computer systems14 Decision Trees Decision tree using : n Square for an action n Circle for a condition