DESCRIBING PROCESS SPECIFICATIONS AND STRUCTURED DECISIONS

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CHAPTER 11 DESCRIBING PROCESS SPECIFICATIONS AND
STRUCTURED DECISIONS
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DIFFERENT METHODS FOR DECISION ANALYSIS AND
PROCESS LOGIC DESCRIPTION ARE

• STRUCTURED ENGLISH
• DECISION TABLES
• DECISION TREES

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PROCESS SPECIFICATIONS ARE PREPARED FOR PROCESSES
TO SHOW THE LOGIC AND FORMULAS THAT TRANSFORM
INPUT DATA INTO OUTPUT DATA.

• GOALS OF PROCESS SPECIFICATIONS
• REDUCE AMBIGUITY OF THE PROCESS
• OBTAIN A PRECISE DESCRIPTION OF WHAT IS
  ACCOMPLISHED
• VALIDATE THE SYSTEM DESIGN

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VARIABLES REQUIRED FOR STRUCTURED DECISIONS

• CONDITIONS
• CONDITION ALTERNATIVES
• ACTIONS
• ACTION RULES

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STRUCTURED ENGLISH IS A MODIFIED FORM OF ENGLISH
USED TO SPECIFY THE LOGIC OF INFORMATION SYSTEM
PROCESSES. STRUCTURED ENGLISH TYPICALLY RELIES
ON ACTION VERBS AND NOUN PHRASES AND CONTAINS NO
ADJECTIVES OR ADVERBS. STRUCTURED ENGLISH IS
USED WHEN THE PROCESS LOGIC IN NOT COMPLEX.
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ADVANTAGES OF STRUCTURED ENGLISH

• CLARIFIES THE LOGIC AND RELATIONSHIPS FOUND IN
  HUMAN ENGLISH
• IT REPRESENTS THE PROCESSES IN A SHORTHAND MANNER
  THAT IS RELATIVELY EASY FOR USERS TO UNDERSTAND.

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RULES FOR WRITING STRUCTURED ENGLISH

• THE LOGIC OF ALL PROCESSES IN A SYSTEM IS
  EXPRESSED AS A COMBINATION OF SEQUENTIAL,
  DECISION, CASE AND REPETITION STRUCTURES.
• KEY WORDS SUCH AS IF, THEN, ELSE, DO, DO WHILE,
  PERFORM, AND DO UNTIL SHOULD BE CAPITALIZED AND
  STRUCTURES SHOULD BE INDENTED TO SHOW THEIR
  LOGICAL HIERARCHY.
• WHERE A WORD OR PHRASE IS USED, WHICH IS DEFINED
  IN A DATA DICTIONARY, THE WORD OR PHRASE SHOULD
  BE UNDERLINED.

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TYPES OF CONSTRUCTS USED IN STRUCTURED ENGLISH

• SEQUENTIAL INSTRUCTIONS THIS STRUCTURE COVERS
  ANY INSTRUCTIONS THAT HAS NO REPETITION OR
  BRANCHING BUILT INTO IT.
• DECISION INSTRUCTIONS THIS STRUCTURE INCLUDES A
  CONDITION THAT HAS TO BE MET BEFORE AN ACTION IS
  PERFORMED I.E. IF A CONDITION IS TRUE THEN TAKE
  A PARTICULAR ACTION OTHERWISE MOVE TO THE ELSE.

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TYPES OF CONSTRUCTS USED IN STRUCTURED ENGLISH

• CASE DECISION INSTRUCTIONS A SPECIAL KIND OF
  DECISION STRUCTURE ARISES WHEN THERE ARE SEVERAL
  POSSIBILITIES OF A CONDITION WHICH NEVER OCCUR IN
  THE COMBINATION I.E. THEY REPRESENT DIFFERENT
  CASES WHICH ARE MUTUALLY EXCLUSIVE.
• REPETITION (LOOP) INSTRUCTIONS THIS STRUCTURE
  APPLIES TO ANY SITUATION IN WHICH AN INSTRUCTION
  OR A GROUP OF INSTRUCTIONS IS REPEATED UNTIL SOME
  DESIRED RESULT IS OBTAINED.

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DECISION TABLE A MATRIX REPRESENTATION OF THE
LOGIC OF A DECISION, WHICH SPECIFIES THE POSSIBLE
CONDITIONS FOR THE DECISION AND THE RESULTING
ACTIONS.

• CONDITION STUBS
• ACTION STUBS
• RULES

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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   RULES THAT PRAT OF A
DECISION TABLE THAT SPECIFIES WHICH ACTIONS ARE
TO BE FOLLOWED FOR A GIVEN SET OF CONDITIONS
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PROCEDURES FOR BUILDING THE DECISION TABLE

• THE NUMBER OF CONDITIONS THAT MAY AFFECT THE
  DECISION WILL BE THE NUMBER OF ROWS IN THE TOP
  HALF OF THE DECISION TABLE.
• THE NUMBER OF ACTIONS WILL BE THE NUMBER OF ROWS
  IN THE LOWER HALF OF THE TABLE.
• THE NUMBER OF COLUMNS OR RULES IN A DECISION
  TABLE IS CALCULATED BY MULTIPLYING THE NUMBER OF
  ALTERNATIVE FOR EACH CONDITION.

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PROCEDURES FOR BUILDING THE DECISION TABLE

• FILL IN THE CONDITION ALTERNATIVES.
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• TAKE THE LAST CONDITION AND ALTERNATE ITS
  POSSIBILITIES ALL ALONG THE ROW
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• NOTE HOW OFTEN THE PATTERN REPEATS ITSELF. TAKE
  THE CONDITION IMMEDIATELY ABOVE THE ONE YOU JUST
  FILLED IN AND COVER EACH PATTERN GROUP WITH A
  VALUE FOR THIS NEXT CONDITION, REPEATING AS
  NEEDED.

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PROCEDURES FOR BUILDING THE DECISION TABLE

• SIMPLIFY THE DECISION TABLE IF POSSIBLE. LOOK FOR
  PATTERNS IN THE RULES, ESPECIALLY FOR INDIFFERENT
  CONDITIONS AND USE THE FOLLOWING TECHNIQUES TO
  CONSOLIDATE THE TABLE
• A. FIND A PAIR OF RULES FOR WHICH THE ACTION IS
  THE SAME THE CONDITION VALUES ARE THE SAME
  EXCEPT FOR ONE AND ONLY ONE CONDITION WHERE THEY
  ARE DIFFERENT.
• B. REPLACE THAT PAIR WITH A SINGLE RULE USING
  THE INDIFFERENCE SYMBOL ( ) FOR THE ONLY
  CONDITION WHICH WAS DIFFERENT.
• C. REPEAT FOR ANY OTHER PAIR WHICH MEETS THE
  CRITERIA.
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• CHECK THE TABLE FOR ANY IMPOSSIBLE SITUATIONS,
  CONTRADICTIONS, AND REDUNDANCIES.

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• DECISION TREE IS A GRAPHICAL TECHNIQUE THAT
  DEPICTS A DECISION OR CHOICE SITUATION AS A
  CONNECTED SERIES OF NODES AND BRANCHES. THE
  DECISION TREE HAS TWO COMPONENTS
• DECISION POINTS OR CONDITION WHICH ARE
  REPRESENTED BY NODES
• ACTIONS WHICH ARE REPRESENTED BY SQUARES.

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CRITERIA FOR DECIDING AMONG STRUCTURED ENGLISH,
DECISION TABLES, AND DECISION TREES
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CRITERIA FOR DECIDING BETWEEN DECISION TABLES AND
DECISION TREES