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3 - Chapter 3 Systems Development Systems and Documentation...

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Unformatted text preview: Chapter 3 Systems Development Systems and Documentation Techniques Learning Objectives Learning Prepare and use data flow diagrams Prepare Draw flowcharts In order to understand, evaluate, and design In information systems information Introduction Introduction A clear understanding of the system is a precondition for Operation Internal control evaluation Methods of describing systems Graphical methods Data Flow Diagrams (DFDs) Flow charts (document & system) Program flow charts (not covered in this course) Written descriptions Combination of a graphical methods and written Combination descriptions descriptions Documentation Skill Levels Read To understand how a system operates To understand job tasks and responsibilities Evaluate System of internal controls Identify strengths and weaknesses Design audit program Recommend improvements Proposed systems Prepare System of internal controls description System implementation proposals Documentation Tools Data flow diagram: Data Document flow chart: System flow chart: Program flow chart: Data Flow Diagrams Graphically describe data flows Elements Data Flow Diagram Symbols Data Symbol Name Data sources and destinations Explanation People & organizations that send data to and receive data from the systems Storage of data Data stores Transformation processes Transformation of data from inputs to outputs Flow of the data into or out of a source, destination, store or process Data flows Sales Order Processing DFD Sales Context Diagram Sales Order Processing DFD Sales DFD Guidelines Understand the system Observe Interview Ignore Control processes Control actions Determine system boundaries Include all relevant items Exclude irrelevant items If in doubt, include (review later) DFD Guidelines (cont.) Identify data flows entering or exiting a system’s Identify boundary boundary All data flows come from and go to either a Transformation processes Data store (file) Data source Data destination Data flows can be Unidirectional Bidirectional DFD Guidelines (cont.) Identify data transformation processes Processes transform data into information All processes should have one or more incoming and outgoing data All flows flows Group transformation processes that Are logically related Or occur at the same time and place Describe all data stores (files) Identify all data stores Identify all data flows that enter or exit a data store DFDs do not identify the storage medium Name all DFD elements Use verbs & verb phrases to name processes Use nouns & noun phrases to name everything else DFD Guidelines (cont.) Subdivide the DFD if more than 5-7 processes Give each process a sequential number Data should flow from lower to higher numbered processes Exception: bidirectional flows Repeat the process until refined Prepare a final copy Data flow lines should not cross Include on each page • • • DFD name Preparer’s name Date Subdividing the DFD DFDs are subdivided into successively lower levels with DFDs greater detail greater The highest level is refered to as a ___________. Summary level view Depicts • The system • Entities that are sources and destinations of inputs and Entities outputs outputs Document Flow Charts Describe ________ systems Graphically portray document flows “Cradle to grave” System Flow Charts Portray systems that have both __________________ Portray components components Input Processing Output Disk Tape Terminals etc. Also describe media used by the system Basic Flow Chart Symbols Basic Symbol Represents Start & end points Paper document Multi-part paper document Manual input Decision Computer display Computer process Symbol Represents Computer disk data storage Direct access storage T T Document file (Temporary, On-page connector Off-page connector Manual process Flow by Date, by NAme, by Number) See Microsoft Excel Autoshapes for more Flowchart Guidelines Understand the system Observe Interview Identify the entities Divide the flowchart into columns Flow proceeds generally from top to bottom, left to right Clear beginning and ending Manual processing should have an input and output No direct connection of two documents A document moving between columns should be shown in document both columns both Flowchart Guidelines (cont) Use connectors On-page connectors avoid excessive lines Off-page connectors move among pages Manual processes are not needed to show Manual no Forwarded documents Documents entering a file Data stored or retrieved from a computer file should pass Data through a processing operation (program) first through Use an iterative process Start with a rough sketch Redesign to avoid clutter and crossed lines Verify accuracy Identify each page with flowchart name, date, and preparer’s name Amusement Park Maintenance Flowchart Example Amusement (see separate Lecture Guide file on WebCT for a more readable version) RIDE OPERATIONS RIDE OPERATOR JRU GENERAL MANAGER SERVICE REQUEST 2 MAINTENANCE A SERVICE REQUEST 2 SERVICE REQUEST 2 ACCOUNTING B WORK ORDER 4 PREPARE SVC REQUEST APPROVE? SERVICE REQUEST 1 2 YES NO PREPARE W ORK ORDER COST & PREPARE SUM REPAIR TYPE? WORK ORDER 2 3 4 1 SERVICE REQUEST 2 WRK ORDER SUMMARY 2 1 3 WORK ORDER 4 MAINTENANCE YES APPROVE? A C RECORD MAT'LS & LABOR NO C SERVICE REQUEST 2 WORK ORDER 2 N WORK ORDER 3 4 C N N B Prepared by: J.B. Stinson Prepared on: 5/5/2005 Last revised on: none END OF CHAPTER 3 END ...
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