Question 1 1. A data flow element in a DFD must be conntected.docx

Question 1
1.
A data flow element in a DFD must be conntected at both ends.
Answer
True
False
1 points
Question 2
1.
Data Flow Diagrams are intended to be used with one very
specific programming language.
Answer
True
False
1 points
Question 3
1.
Which of these defines the boundaries of a system?
Answer
Physical Process
Logical Process
Data Dictionary
Context Diagram
1 points
Question 4

1.
A very useful information gathering tool which helps the
analyst understand processes and create a DFD or part of a DFD
is called a(n)
Answer
programming kit
digital camera
use case
sample case
1 points
Question 5
1.
The term 'CRUD' when used in DFD context outlines anything
that can be done to:
Answer
system users
the software application which will be developed
processes in a top level diagram
records in a data store
1 points

Question 6
1.
A data flow symbol in a DFD can be connected to a process, a
data store, or an external entity.
Answer
True
False
1 points
Question 7
1.
An advantage to using DFD's is that the analyst does not have to
communicate with users or programmers.
Answer
True
False
1 points
Question 8
1.
The following processes are modeled in a DFD:
1) Customer picking up item from shelf
2) Cashier ringing up item on cash register
3) Customer offering cash or credit card
This diagram is a(n) ___________ DFD
Answer
Physical
Logical
Merchant
Financial

1 points
Question 9
1.
A low level process in a DFD (one that will not be exploded or
broken down any further is called a(n)
Answer
cornerstone
primitive
primary
core
1 points
Question 10
1.
A process with a number of '0' is alway associated with a(n)
Answer
site map
context diagram
inactive process
terminated process

Kendall & Kendall Copyright © 2014 Pearson Education, Inc.
Publishing as Prentice Hall
7
Kendall & Kendall
Systems Analysis and Design, 9e
Using Data Flow Diagrams
*
*
7-*
Learning ObjectivesComprehend the importance of using logical
and physical data flow diagrams (DFDs) to graphically depict
movement for humans and systems in an organization.Create,

use, and explode logical DFDs to capture and analyze the
current system through parent and child levels.Develop and
explode logical DFDs that illustrate the proposed
system.Produce physical DFDs based on logical DFDs you have
developed.Understand and apply the concept of partitioning of
physical DFDs.
*
7-*
Data Flow DiagramsGraphically characterize data processes and
flows in a business systemDepict:System
inputsProcessesOutputs
*
A series of layered data flow diagrams may be used to represent
and analyze detailed procedures in the larger system.
7-*
Major TopicsData flow diagram symbolsData flow diagram
levelsCreating data flow diagramsPhysical and logical data flow
diagramsPartitioningCommunicating using data flow diagrams

*
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Advantages of the Data Flow ApproachFreedom from
committing to the technical implementation too
earlyUnderstanding of the interrelatedness of systems and
subsystemsCommunicating current system knowledge to
usersAnalysis of the proposed system
*
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Basic SymbolsA double square for an external entityAn arrow
for movement of data from one point to anotherA rectangle with
rounded corners for the occurrence of a transforming processAn
open-ended rectangle for a data store
*
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The Four Basic Symbols Used in Data Flow Diagrams, Their
Meanings, and Examples
(Figure 7.1)
*
An entire system and numerous subsystems can be depicted
graphically with these four symbols in combination.
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External EntitiesRepresent another department, a business, a
person, or a machineA source or destination of data, outside the
boundaries of the systemShould be named with a noun
*
An external entity (outside the boundaries of the system) sends
data to (source) or receives data from (destination) the system.
Each entity is labeled with a name, generally a noun.
The same entity may be used more than once on a given data
flow diagram.
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Data FlowShows movement of data from one point to
anotherDescribed with a nounArrowhead indicates the flow

directionRepresents data about a person, place, or thing
*
Data flows occurring simultaneously can be depicted doing just
that through the use of parallel arrows.
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ProcessDenotes a change in or transformation of dataRepresents
work being performed in the systemNaming convention:Assign
the name of the whole system when naming a high-level
processTo name a major subsystem attach the word subsystem
to the nameUse the form verb-adjective-noun for detailed
processes
*
The data flow leaving a process is always labeled differently
then the data flow entering the process.
A process must also be given a unique identifying number
indicating its level in the diagram.
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Data StoreA depository for data that allows examination,
addition, and retrieval of dataNamed with a noun, describing the
dataData stores are usually given a unique reference number,
such as D1, D2, D3 Represents a:DatabaseComputerized

fileFiling cabinet
*
Data stores represent a person, place, or thing which is why
they are named with a noun.
Temporary data stores, such as scratch paper or a temporary
computer file are not included on the data flow diagram.
7-*
Steps in Developing Data Flow Diagrams
(Figure 7.2)
*
Data flow diagrams can and should be drawn systematically.
To begin a data flow diagram, collapse the organization’s
system narrative into a list with four categories of external
entity, data flow, process, and data store. This list helps
determine the boundaries of the system. Next begin drawing the
context diagram.
7-*
Creating the Context DiagramThe highest level in a data flow

diagramContains only one process, representing the entire
systemThe process is given the number 0All external entities, as
well as major data flows are shown
*
Basically the context diagram consists of:one process—
depicting the entire systemexternal entitiesdata flows from the
external entities to the process
The diagram does not contain any data stores.
7-*
Basic RulesThe data flow diagram must have one processMust
not be any freestanding objectsA process must have both an
input and output data flowA data store must be connected to at
least one processExternal entities should not be connected to
one another
*
7-*
Context Diagram (Figure 7.3)

*
7-*
Drawing Diagram 0The explosion of the context diagramMay
include up to nine processesEach process is numberedMajor
data stores and all external entities are included
*
Including more than nine processes will result in a cluttered
diagram that is difficult to understand.
Each process is numbered with an integer, starting form the
upper left-hand corner and working toward the lower right-hand
corner.
Because a data flow diagram is two-dimensional, you can start
at any point and work forward or backward through the
diagram.
7-*
Drawing Diagram 0 (continued)Start with the data flow from an
entity on the input sideWork backward from an output data
flowExamine the data flow to or from a data storeAnalyze a
well-defined processTake note of any fuzzy areas
*

Because a data flow diagram is two-dimensional, you can start
at any point and work forward or backward through the
diagram.
7-*
Note Greater Detail in Diagram 0
(Figure 7.3)
*
7-*
Data Flow Diagram LevelsData flow diagrams are built in
layersThe top level is the context levelEach process may
explode to a lower levelThe lower level diagram number is the
same as the parent process numberProcesses that do not create a
child diagram are called primitive
*

7-*
Creating Child DiagramsEach process on diagram 0 may be
exploded to create a child diagramA child diagram cannot
produce output or receive input that the parent process does not
also produce or receiveThe child process is given the same
number as the parent processProcess 3 would explode to
Diagram 3
*
The process on Diagram 0 that is exploded is called the parent
process, and the diagram that results is called the child diagram.
On Diagram 3, the processes would be numbered 3.1, 3.2, 3.3,
and so on. This allows the analyst to trace a series of processes
through many levels of explosion.
7-*
Creating Child Diagrams (continued)Entities are usually not
shown on the child diagrams below Diagram 0If the parent
process has data flow connecting to a data store, the child
diagram may include the data store as wellWhen a process is not
exploded, it is called a primitive process
*
In addition, the lower-level diagram may contain data stores
not shown on the parent process.

7-*
Differences between the Parent Diagram (above) and the Child
Diagram (below) (Figure 7.4)
*
7-*
Data Flow Diagrams Error SummaryForgetting to include a data
flow or pointing an arrow in the wrong directionConnecting
data stores and external entities directly to each
otherIncorrectly labeling processes or data flow
*
7-*
Data Flow Diagrams Error Summary (continued)Including more
than nine processes on a data flow diagram Omitting data
flowCreating unbalanced decomposition (or explosion) in child
diagrams
*

7-*
Checking the Diagrams for Errors (Figure 7.5)Forgetting to
include a data flow or pointing an arrow in the wrong direction
*
7-*
Checking the Diagrams for Errors (continued Figure
7.5)Connecting data stores and external entities directly to each
other
*
7-*
Typical Errors that Can Occur in a Data Flow Diagram (Payroll
Example) (continued Figure 7.5)

*
7-*
Logical and Physical Data Flow DiagramsLogicalFocuses on the
business and how the business operatesNot concerned with how
the system will be constructedDescribes the business events that
take place and the data required and produced by each event
*
7-*
Logical and Physical Data Flow DiagramsPhysicalShows how
the system will be implementedDepicts the system
*
7-*
Features Common of Logical and Physical Data Flow Diagrams

(Figure 7.7)
*
7-*
The Progression of Models from Logical to Physical (Figure
7.8)
*
The progression of creating data flow diagrams is:Analyze the
current system (current logical DFD).Add features the new
system should include (the proposed logical DFD).Finally the
best methods for implementing the new system should be
developed (the physical DFD).
7-*
Logical Data Flow Diagram Example (Figure 7.9)
*

7-*
Physical Data Flow Diagram Example (Figure 7.9)
*
7-*
Developing Logical Data Flow DiagramsBetter communication
with usersMore stable systemsBetter understanding of the
business by analystsFlexibility and maintenanceElimination of
redundancy and easier creation of the physical model
*
Better communication with users—centered on business
activities.
More stable systems—based on business events and not on a
particular technology or method of implementation.
7-*
Developing Physical Data Flow DiagramsClarifying which
processes are performed by humans and which are
automatedDescribing processes in more detailSequencing
processes that have to be done in a particular orderIdentifying
temporary data stores Specifying actual names of files and

printoutsAdding controls to ensure the processes are done
properly
*
7-*
Physical Data Flow Diagrams Contain Many Items Not Found in
Logical Data Flow Diagrams (Figure 7.10)
*
Physical data flow diagrams are often more complex than
logical data flow diagrams simply because of the many data
stores present in the system.
The acronym CRUD is used for Create, Read, Update, and
Delete.
A CRUD matrix shows which programs or processes add, read,
update, or delete master file records.
Intermediate data stores—consist of transaction files used to
store data between processes.
A physical data flow diagram may appear more linear that a
logical model.

7-*
CRUD MatrixThe acronym CRUD is often used
forCreateReadUpdateDeleteThese are the activities that must be
present in a system for each master fileA CRUD matrix is a tool
to represent where each of these processes occurs in a system
*
7-*
CRUD Matrix (Figure 7.11)
*
7-*
Event Modeling and Data Flow DiagramsAn input flow from an
external entity is sometimes called a trigger because it starts the
activities of a processEvents cause the system to do something
and act as a trigger to the systemAn approach to creating
physical data flow diagrams is to create a data flow diagram
fragment for each unique system event

*
Triggers start activities or processes, which in turn use data or
produce output.
7-*
Event Response TablesAn event table is used to create a data
flow diagram by analyzing each event and the data used and
produced by the eventEvery row in an event table represents a
data flow diagram fragment and is used to create a single
process on a data flow diagram
*
7-*
An Event Response Table for an Internet Storefront (Figure
7.12)
*
7-*

Data Flow Diagrams for the First Three Rows of the Internet
Storefront Event Response Table (Figure 7.13)
*A dataflow diagram fragment is represented by one row in the
table.Each DFD fragment is a single process on a data flow
diagram.All the fragments are then combined to form Diagram
0.The trigger and response column becomes the input and output
data flows.The activity becomes the process.The data stores are
determined by examining the input and output data flows.
The advantage of building data flow diagrams based on
events is that the users are familiar with the events that take
place in their business area and know how the events drive other
activities.
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Use Cases and Data Flow DiagramsEach use case defines one
activity and its trigger, input, and outputAllows the analyst to
work with users to understand the nature of the processes and
activities and then create a single data flow diagram fragment
*
7-*
Partitioning Data Flow DiagramsPartitioning is the process of

examining a data flow diagram and determining how it should
be divided into collections of manual procedures and computer
programsA dashed line is drawn around a process or group of
processes that should be placed in a single computer program
*
Analyze each process to determine whether it should be a
manual or automated procedure.
Group automated procedures into a series of computer
programs.
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Reasons for PartitioningDifferent user groupsTimingSimilar
tasksEfficiencyConsistency of dataSecurity
*
Different user groups—are the processes performed by several
different user groups, often at different physical locations in the
company? If so, they should be partitioned into different
computer programs.
Timing—processes that execute at different times must be in
separate programs
Similar tasks—may be included in the same program.
Efficiency—several batch processes may be included in the
same program for efficiency.
Consistency—several processes may be included in the same
program or job stream for consistency of data.
Security—may be partitioned into different programs for
security reasons.

7-*
Partitioning WebsitesImproves the way humans use the
siteImproves speed of processingEase of maintaining the
siteKeep the transaction secure
*
Each time data must be obtained from a data store or an external
partner, a website designer might consider creating a unique
Web form and DFD process to validate and process the data or
may also use Ajax, sending a request to the server and obtain a
small amount of data or an XML document returned to the same
page.
7-*
Communicating Using
Data Flow Diagrams
Use unexploded data flow diagrams early when ascertaining
information requirementsMeaningful labels for all data
components
*
Use unexploded data flow diagrams early when ascertaining
information requirements—at this stage they can provide an
overview of data movement through the system, lending a visual

perspective unavailable in narrative data.
Meaningful labels for all data components—labels should not be
generic.
Data flow diagrams can be used for documenting high and low
levels of analysis and helping to substantiate the logic
underlying the data flows of the organizations.
7-*
SummaryData flow diagramsStructured analysis and design
tools that allow the analyst to comprehend the system and
subsystems visually as a set of interrelated data flowsDFD
symbolsRounded rectangleDouble squareAn arrowOpen-ended
rectangle
*
7-*
Summary (continued)Creating the logical DFDContext-level
data flow diagramLevel 0 logical data flow diagramChild
diagramsCreating the physical DFDCreate from the logical data
flow diagramPartitioned to facilitate programming

*
7-*
Summary (continued)Partitioning data flow diagramsWhether
processes are performed by different user groupsProcesses
execute at the same timeProcesses perform similar tasksBatch
processes can be combined for efficiency of dataProcesses may
be partitioned into different programs for security reasons
*
7-*
Copyright © 2014 Pearson Education, Inc.
*

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