Systems Documentation TechniquesSystems Documentation Techniques

Professor Merle MartinProfessor Merle MartinProfessor Yan XiongProfessor Yan XiongCollege of BusinessCollege of BusinessCSU SacramentoCSU Sacramento

2/6/0232/6/023

AgendaAgenda Why Document SystemWhy Document System Data Flow DiagramsData Flow Diagrams FlowchartsFlowcharts Difference between DFDs and Difference between DFDs and

FlowchartsFlowcharts

Why Document Systems?Why Document Systems? User confidence that you understand User confidence that you understand

systemsystem Successive refinement of detail down Successive refinement of detail down

to programming levelto programming level Ease of Program Maintenance, Ease of Program Maintenance,

System Modification, Reengineering, System Modification, Reengineering, and Replacement and Replacement

Why Document Systems?Why Document Systems? Problem SolvingProblem Solving Humans solve complex Humans solve complex

problems byproblems by breaking them into smaller and breaking them into smaller and

smaller modulessmaller modules until they fit into the human minduntil they fit into the human mind solving the modular sub-problemssolving the modular sub-problems aggregating small solutions aggregating small solutions

into total solutioninto total solution

AgendaAgenda Why Document Accounting Why Document Accounting

Information SystemsInformation Systems Data Flow Diagrams (DFDs)Data Flow Diagrams (DFDs) FlowchartsFlowcharts Difference between DFDDifference between DFD

Data Flow DiagramsData Flow Diagrams Data flow diagram (DFD) graphically describes flow Data flow diagram (DFD) graphically describes flow

of data within any system of data within any system Used to document existing systems and to plan and design new Used to document existing systems and to plan and design new

onesones No ideal way to develop a DFDNo ideal way to develop a DFD

judgment within standard rulesjudgment within standard rules

Data Flow DiagramsData Flow Diagrams DFD composed of only four elements:DFD composed of only four elements: Data sources and destinations: Data sources and destinations: External Entities External Entities

Another organization/organization unit which Another organization/organization unit which exchanges data with the focal systemexchanges data with the focal system

A person who interacts with the system A person who interacts with the system (customer of a banking system)(customer of a banking system)

Another information systemAnother information system Data FlowsData Flows ProcessesProcesses Data Stores: Data Stores: Temporary or permanent repository Temporary or permanent repository

of dataof data

DFD SymbolsDFD Symbols

ExternalEntity

ExternalEntity

SourceSource

ExternalEntity

ExternalEntity

SinkSink

ProcessProcessDataFlowDataFlow

DataFlowDataFlow

DataStoreDataStore

Data FlowData Flow

INPUTINPUT PROCESSPROCESS OUTPUTOUTPUT

DFD SymbolsDFD Symbols

1.1ProcessPayment

1.1ProcessPayment

CustomerCustomer

SourceSource

PaymentPaymentBankBank

SinkSink

depositdeposit

Customer File

Customer File

Remittance dataRemittance data

Data Flow Diagrams ExplosionData Flow Diagrams Explosion Data flow diagrams subdivided into Data flow diagrams subdivided into

successively lower levels in order to provide successively lower levels in order to provide increasing amounts of detailincreasing amounts of detail

This decomposition process is called This decomposition process is called “explosion”“explosion”

Data Flow Diagram ExplosionData Flow Diagram Explosion Context LevelContext Level Ist Level ExplosionIst Level Explosion 22ndnd Level Explosion Level Explosion Succeeding levels as necessarySucceeding levels as necessary Until reach Until reach primitive levelprimitive level

Ready to codeReady to code

Context DiagramContext Diagram Includes onlyIncludes only

External EntitiesExternal Entities Data FlowsData Flows

All elements included on Context All elements included on Context Diagram Diagram mustmust be included be included somewheresomewhere on lower level diagrams on lower level diagrams

Data stores rarely included!Data stores rarely included!

Context DiagramContext Diagram Why discourage Data Stores on Why discourage Data Stores on

Context Diagram? Context Diagram? Author includes themAuthor includes them

Context Diagram shows interaction Context Diagram shows interaction of your system with outside worldof your system with outside world

Data Stores are Data Stores are INSIDEINSIDE your system, your system, not in outside worldnot in outside world

0Purcha-

sing

0Purcha-

sing

InventorySystem

InventorySystem

PurchaseRequisitionPurchaseRequisition

OrderEntry

System

OrderEntry

System Special OrderSpecial Order

VendorVendor

Purchase OrderPurchase Order

ReceivingSystem

ReceivingSystem

Purchase OrderNotification

Purchase OrderNotification

Context DiagramContext Diagram

11stst Level Explosion Level Explosion Also includes all data Also includes all data

flows and external entitiesflows and external entities Now data stores are addedNow data stores are added Excellent means of confirming Excellent means of confirming

understanding of system between understanding of system between analyst and clientanalyst and client

Each process will be Each process will be explodedexploded into into lower level DFDslower level DFDs

Ist Level ExplosionIst Level Explosion1

EditOrder

3Prepare

P.O.

3Prepare

P.O.

2Set Ship

Mode

2Set Ship

Mode

Inventory Inventory

VendorVendor

P.OrderP.Order ReceivingReceiving

VendorVendor

OrderEntryOrderEntry

InventoryInventory

PurchaseRequisitionPurchaseRequisition

Special

OrderSpecial

Order

Purchase

OrderPurchase

Order

P.O.Noti-ficationP.O.Noti-fication

P.O. CopyP.O. Copy

InfoInfo

StatusStatus

Approved OrderApproved Order

Draft P.ODraft P.O

ProblemOrders

ProblemOrders

ProblemsProblems

22ndnd and Succeeding and Succeeding LevelsLevels Must be consistent with Must be consistent with

parent DFDparent DFD Same external entitiesSame external entities Same data storesSame data stores Same data flowsSame data flows

2nd Level Explosion 2nd Level Explosion (Process 1)(Process 1)

InventoryInventory

1.1Log-inOrder

1.3Approve

Order

1.3Approve

Order

1.2Edit

Order

1.2Edit

Order

OrderEntryOrderEntry

Inventory Inventory

Log-in#s

Log-in#s

PurchaseRequisitionPurchaseRequisition

Special

OrderSpecial

Order

Approved OrderApproved Order

StatusStatus

Logged-in OrderLogged-in Order

Edited OrderEdited Order

ProblemOrders

ProblemOrdersProblemsProblems

Next #

Next #

Process 2.1Process 2.1

DFD Rules -- ProcessDFD Rules -- ProcessA. No process can have only outputs (a miracle)A. No process can have only outputs (a miracle)B. No process can have only inputs (a black hole)B. No process can have only inputs (a black hole)C. Verb phrase labelsC. Verb phrase labels

DFD Rules -- Data StoreDFD Rules -- Data StoreD. Data cannot move directly from one data store D. Data cannot move directly from one data store

to another data store -- it must be moved by a to another data store -- it must be moved by a process.process.

E.E. Data cannot move directly from an outside Data cannot move directly from an outside source to a data store -- it must be moved by a source to a data store -- it must be moved by a process.process.

F.F. Data cannot move directly to an outside sink Data cannot move directly to an outside sink from a data store -- it must be moved by a from a data store -- it must be moved by a process.process.

G. Noun phrase labelG. Noun phrase label

DFD Rules -- Source / SinkDFD Rules -- Source / SinkH.H. Data cannot move directly from a source Data cannot move directly from a source

to a sink. It must be moved by a process.to a sink. It must be moved by a process.I.I. Noun phrase labelNoun phrase label

DFD Rules -- Data FlowDFD Rules -- Data FlowJ.J. A data flow has only one direction of flow between A data flow has only one direction of flow between

symbols; a data flow may flow in both directions to and symbols; a data flow may flow in both directions to and from a data store (usually two symbols)from a data store (usually two symbols)

K.K. A fork in a data flow means that exactly the same data A fork in a data flow means that exactly the same data goes to two different processes or data stores.goes to two different processes or data stores.

DFD Rules -- Data FlowDFD Rules -- Data FlowL. A data flow cannot go directly back to the same process it leavesL. A data flow cannot go directly back to the same process it leavesM. A data flow to a data store means update (delete or change)M. A data flow to a data store means update (delete or change)N. A data flow from a data store means retrieve or useN. A data flow from a data store means retrieve or useO.Noun phrase labelO.Noun phrase label

Other DFD IssuesOther DFD Issues Two additional guidelinesTwo additional guidelines

Inputs to a process are different from outputs Inputs to a process are different from outputs of that processof that process

Every process in a DFD has a unique nameEvery process in a DFD has a unique name

ExerciseExerciseDraw a Context Diagram and a 1Draw a Context Diagram and a 1stst level explosion level explosionCurrent System Description for the payroll system at No-Wear Products.Current System Description for the payroll system at No-Wear Products. Time data are recorded in each department using time cards and Time data are recorded in each department using time cards and

clocks.clocks. The time data are sent to the payroll by different departments.The time data are sent to the payroll by different departments. Payroll clerks review the time data for their completeness.Payroll clerks review the time data for their completeness. Human resources send the payroll data on personnel changes, such Human resources send the payroll data on personnel changes, such

as increases in pay rates and new employees.as increases in pay rates and new employees. Payroll clerks update the payroll file based on these changes.Payroll clerks update the payroll file based on these changes. At the end of the period, payroll clerks enter the time card data into At the end of the period, payroll clerks enter the time card data into

the payroll file for processing. The payroll supervisor reviews the file the payroll file for processing. The payroll supervisor reviews the file and makes necessary corrections.and makes necessary corrections.

Payroll clerks send the direct payments to the bank and also the Payroll clerks send the direct payments to the bank and also the direct deposit slips to the departments.direct deposit slips to the departments.

AgendaAgenda Why Document Accounting Why Document Accounting

Information SystemsInformation Systems Data Flow DiagramsData Flow Diagrams FlowchartFlowchart Difference between DFD and Difference between DFD and

FlowchartFlowchart

FlowchartsFlowcharts A flowchart is an analytical technique used to describe A flowchart is an analytical technique used to describe

some aspect of an information system in a clear, concise, some aspect of an information system in a clear, concise, and logical manner.and logical manner.

Flowcharts use a standard set of symbols to pictorially Flowcharts use a standard set of symbols to pictorially describe transaction processing procedures.describe transaction processing procedures.

Flowchart SymbolsFlowchart Symbols Flowcharting symbols can be divided into the following four categories:Flowcharting symbols can be divided into the following four categories:

1 Input/output symbolsInput/output symbols2 Processing symbolsProcessing symbols3 Storage symbolsStorage symbols4 Flow and miscellaneous symbolsFlow and miscellaneous symbols

Flowcharting Symbols: Flowcharting Symbols: Input Output SymbolsInput Output Symbols

Document

Online keying

Display

Input/output; Journal/ledger

Symbol Name

Flowchart Symbols: Flowchart Symbols: Processing symbolsProcessing symbols

Manual operations

Computer processing

Auxiliary operation

Symbol Name

Flowchart Symbols: Flowchart Symbols: Storage SymbolsStorage Symbols

Magnetic disk

Magnetic tape

Symbol Name

Flowchart Symbols: Flow and Flowchart Symbols: Flow and miscellaneous Symbolsmiscellaneous Symbols

On-page connector

Off-page connector

Terminal

Decision

Document or processing flowSymbol Name

What are Document Flowcharts?What are Document Flowcharts?

A document flowchart illustrates the flow of documents and A document flowchart illustrates the flow of documents and information between areas of responsibility within an organization.information between areas of responsibility within an organization.

A document flowchart is particularly useful in analyzing the adequacy A document flowchart is particularly useful in analyzing the adequacy of control procedures.of control procedures.

Flowcharts that describe and evaluate internal controls are often Flowcharts that describe and evaluate internal controls are often referred to as referred to as internal control flowcharts.internal control flowcharts.

What are ComputerWhat are ComputerSystem Flowcharts?System Flowcharts?

SystemSystem flowchartsflowcharts depict the relationship among the input, depict the relationship among the input, processing, and output of an AIS.processing, and output of an AIS.

A system flowchart begins by identifying both the inputs that A system flowchart begins by identifying both the inputs that enter the system and their origins.enter the system and their origins.

The input is followed by the processing portion of the flowchart.The input is followed by the processing portion of the flowchart.

What are ComputerWhat are ComputerSystem Flowcharts?System Flowcharts? The resulting new information is the output The resulting new information is the output

component.component. System flowcharts are an important tool of System flowcharts are an important tool of

system analysis, design, and evaluation.system analysis, design, and evaluation.

What are ComputerWhat are ComputerSystem Flowcharts?System Flowcharts?

Process

Output

Input

Storage

What are Program Flowcharts?What are Program Flowcharts? A program flowchart describes the specific logic to perform a process A program flowchart describes the specific logic to perform a process

shown on a systems flowchart.shown on a systems flowchart. A flow line connects the symbols and indicates the sequence of A flow line connects the symbols and indicates the sequence of

operations.operations. The processing symbol represents a data movement or arithmetic The processing symbol represents a data movement or arithmetic

calculation.calculation.

What are Program Flowcharts?What are Program Flowcharts?

Input data

If a condition is met No

Yes

Perform calculation

Update record

What are Program Flowcharts?What are Program Flowcharts? The input/output symbol represents either reading of input or writing The input/output symbol represents either reading of input or writing

of output.of output. The decision symbol represents a comparison of one or more The decision symbol represents a comparison of one or more

variables and the transfer of flow to alternative logic paths.variables and the transfer of flow to alternative logic paths. All points where the flow begins or ends are represented by the All points where the flow begins or ends are represented by the

terminal symbol.terminal symbol.

Flowchart for ProcessingFlowchart for ProcessingCredit OrdersCredit Orders

Entersalesorder

Approvedfor credit?

Rejectorder

Inventoryavailable?

Back-order

Fill order Stop

Start

No

Yes

Yes

No

Example-FlowchartsExample-Flowcharts The Dewey Construction Company processes its The Dewey Construction Company processes its

payroll transactions to update both its payroll master payroll transactions to update both its payroll master file and its work-in-process master file in the same file and its work-in-process master file in the same computer run. Both the payroll master file and the work-computer run. Both the payroll master file and the work-in-process master file are maintained on disk and in-process master file are maintained on disk and accessed directly.accessed directly.

Data to be input to this system are keyed onto a tape Data to be input to this system are keyed onto a tape using a key-to-tape encoder. This tape is then using a key-to-tape encoder. This tape is then processed to update the files. This processing run also processed to update the files. This processing run also produces a payroll register on magnetic tape, employee produces a payroll register on magnetic tape, employee paychecks and earnings statements, and a printed paychecks and earnings statements, and a printed report listing error transactions and summary report listing error transactions and summary information.information.Prepare a system flowchart of the process described.Prepare a system flowchart of the process described.

Paycheck

Job TimeTickets

Key toTape

Encodings

Job TimeRecords

Tape

PayrollProcessing

System

PayrollMaster

File

Work inProcessMaster

File

PayrollRegister

EarningsStatement Error

Transactionsand Summary

AgendaAgenda Why Document Accounting Why Document Accounting

Information SystemsInformation Systems Data Flow DiagramsData Flow Diagrams FlowchartFlowchart Difference between DFD and Difference between DFD and

FlowchartFlowchart

Differences Between DFDs and Differences Between DFDs and FlowchartsFlowcharts

DFDs emphasize the flow of data and what is happening in DFDs emphasize the flow of data and what is happening in a system, whereas a flowchart emphasizes the flow of a system, whereas a flowchart emphasizes the flow of documents or records containing data.documents or records containing data.

A DFD represents the logical flow of data, whereas a A DFD represents the logical flow of data, whereas a flowchart represents the physical flow of data.flowchart represents the physical flow of data.

Differences Between DFDs and Differences Between DFDs and FlowchartsFlowcharts Flowcharts are used primarily to document existing systems.Flowcharts are used primarily to document existing systems. DFDs, in contrast, are primarily used in the design of new DFDs, in contrast, are primarily used in the design of new

systems and do not concern themselves with the physical systems and do not concern themselves with the physical devices used to process, store, and transform data.devices used to process, store, and transform data.