PI2134 Software Engineering
IT Telkom
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Describe data and process modeling concepts
and tools, including data flow diagrams, a data
dictionary, and process descriptions
Describe the symbols used in data flow
diagrams and explain the rules for their use
Draw data flow diagrams in a sequence, from
general to specific
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Explain how to level and balance a set of data
flow diagrams
Describe how a data dictionary is used and what
it contains
Describe how a process specification is used and
what it contains
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Definition
DFD Symbols
Data Flow Diagram Layers
Creating Set of DFDs
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A data flow diagram (DFD) shows how data
moves through an information system but does
not show program logic or processing steps
Data flow diagrams illustrate how data is
processed by a system in terms of inputs and
outputs.
A set of DFDs provides a
logical model that shows
what the system does,
not how it does it
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DFDs use four basic symbols that represent
processes, data flows, data stores, and entities
 Gane and Sarson symbol set
 Yourdon symbol set
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A process transforms
incoming data flow into
outgoing data flow.
Receives input data and
produces output that has a
different content, form, or
both
Contain the business logic,
also called business rules
Referred to as a black box
Process Notations
Yourdon and Coad
Process Notations
Gane and Sarson
Process Notation
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Data flows are pipelines through
which packets of information flow.
Represents one or more data item
The symbol for a data flow is a line
with a single or double arrowhead
Label the arrows with the name of
the data that moves through it.
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Data stores are
repositories of data in
the system.
They are sometimes
also referred to as files.
Represent data that the
system stores
The physical
characteristics of a
data store are
unimportant because
you are concerned only
with a logical model
Datastore Notations
Yourdon and Coad
Datastore Notations
Gane and Sarson
Datastore Notations
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External entities are objects outside the system,
with which the system communicates.
External entities are sources and destinations of
the system's inputs and outputs.
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Draw data flow
diagrams in several
nested layers.
A single process node on
a high level diagram
can be expanded to
show a more detailed
data flow diagram.
Draw the context
diagram first, followed
by various layers of
data flow diagrams.
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A context diagram is a top level (also known as
Level 0) data flow diagram.
It only contains one process node (process 0) that
generalizes the function of the entire system in
relationship to external entities.
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The first level DFD shows the main processes
within the system.
Each of these processes can be broken into
further processes until you reach pseudocode.
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Create a graphical model of the information
system based on your fact-finding results
Performing three main tasks
◦ Step 1: Draw a context diagram
◦ Step 2: Draw a DFD level 1
◦ Step 3: Draw the lower-level diagrams
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Drawing Guidelines
1. Draw the context diagram so it fits on one page
2. Use the name of the information system as the process
name in the context diagram
3. Use unique names within each set of symbols
4. Do not cross lines
5. Provide a unique name and reference number for each
process
6. Obtain user input and feedback
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Zooms in on the context diagram and shows
major processes, data flows, and data stores
Must retain all the connections that flow into and
out of process
Each process has a reference number
Diverging data flow
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Must use leveling and balancing techniques
Leveling
◦ Uses a series of increasingly detailed DFDs to describe
an information system
◦ Exploding, partitioning, or decomposing
Level 2 DFD from the monitor sensors process
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Ensures that the input and output data flows of
the parent DFD are maintained on the child DFD
Simple rule: the dataflows coming into and
going out of a bubble at one level must
correspond to the dataflows coming into and
going out of an entire figure at the next lower
level which describes that bubble.
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A balanced DFD
Fragment
source:
www.yourdon.com
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An out-of-balance
DFD Fragment
Source:
www.yourdon.com
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Definition
DFD Symbols
Data Flow Diagram Layers
Creating Set of DFDs
 Buatlah
DFD tentang Sistem
Informasi Rumah Sakit
 Buatlah DFD sampai level 2