The document discusses data flow diagrams (DFDs), including their purpose and elements. DFDs model the flow of information through a system using four elements: processes, external entities, data stores, and data flows. They provide a graphical representation of a system that is accessible to both technical and non-technical users. DFDs can diagram current or proposed systems and facilitate analysis, design, and communication with users. Different levels of DFDs exist, with context diagrams providing an overview and Level 0/1 diagrams showing more detailed views of the system. Guidelines help ensure DFDs are constructed correctly.
Refer to the following figure which contains drafts of a context and l.docxlmarie40
Refer to the following figure which contains drafts of a context and level-0 DFD for a University class CHAPTER 7 STRUCTURING SYSTEM PR TABLE 7-2 Rules Governing Data Flow Diagramming Process: A. No process can have only outputs. It would be making data from nothing (a miracle). If an object has only outputs, then it must be a source B. No process can have only inputs (a black hole). If an object has only inputs, then it must be a sink C. A process has a verb phrase label. Data Store: D. Data cannot move directly from one data store to another data store. Data must be moved by a process. E. Data cannot move directly from an outside source to a data store. Data must be moved by a process that receives data from the source and places the data into the data store F. Data cannot move directly to an outside sink from a data store. Data must be moved by a process. G. A data store has a noun phrase label. Source/Sink: H. Data cannot move directly from a source to a sink. It must be moved by a process if the data are of any concern to our system. Otherwise, the data flow is not shown on the DFD 1. A source/sink has a noun phrase label. Data Flow: J. A data flow has only one direction of flow between symbols. It may flow in both directions between a process and a data store to show a read before an update. The latter is usually indicated, however, by two separate arrows because these happen at different times. K. A fork in a data flow means that exactly the same data goes from a common location to two or more different processes, data stores, or sources/sinks (this usually indicates different copies of the same data going to different locations). L. A join in a data flow means that exactly the same data come from any of two or more different processes, data stores, or sources/sinks to a common location. M. A data flow cannot go directly back to the same process it leaves. There must be at least one other process that handles the data flow, produces some other data flow, and returns the original data flow to the beginning process. N. A data flow to a data store means update (delete or change). 0. A data flow from a data store means retrieve or use. P. A data flow has a noun phrase label. More than one data flow noun phrase can appear on a single arrow as long as all of the flows on the same arrow move together as one package. (Source: Based on Celko, 1987.) Guidelines for Drawing DFDs In this section, we will consider additional guidelines for drawing DFDs that extend berond the simple mechanics of drawing diagrams and making sure that the rules listed in Tables 7-2 and 7-3 are followed. These guidelines include (1) completeness, (2) consistency, (3) timing considerations, (4) the iterative nature of drawing DFDs, and (5) primitive DFDs. Completeness The concept of DFD completeness refers to whether you have included in your DFDs all of the components necessary for the system you are modeling. If your DFD contains data flows that do not lead anywhere o.
A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modeling its process aspects.
Why DFD technique is so Popular?
Symbols used in DFD
Constructing DFD Models
Data Dictionary
Developing the DFD model of System
Level O DFD or Context Diagram
Level 1 DFD
Strengths of DFD Model
Weaknesses of DFD Model
A graphical tool, useful for communicating with users, managers, and other personnel.
Used to perform structured analysis to determine logical requirements.
Useful for analyzing existing as well as proposed systems.
Focus on the movement of data between external entities and processes, and between processes and data stores.
A relatively simple technique to learn and use.
Data flow diagram is used in software development. It shows the flow of data through the system. It has many levels but beyond level 2 complexity increases. It is used in software engineering, Business analysis, agile development & system structures etc. It can provide a detailed representation of a system. Used as a part of system documentation file. It is very easy to understand. It has many advantages but can make the programmers little confuse concerning the system & take long time to create
A data flow diagram (DFD) illustrates how data is processed by a system in terms of inputs and outputs. As its name indicates its focus is on the flow of information, where data comes from, where it goes and how it gets stored.
Refer to the following figure which contains drafts of a context and l.docxlmarie40
Refer to the following figure which contains drafts of a context and level-0 DFD for a University class CHAPTER 7 STRUCTURING SYSTEM PR TABLE 7-2 Rules Governing Data Flow Diagramming Process: A. No process can have only outputs. It would be making data from nothing (a miracle). If an object has only outputs, then it must be a source B. No process can have only inputs (a black hole). If an object has only inputs, then it must be a sink C. A process has a verb phrase label. Data Store: D. Data cannot move directly from one data store to another data store. Data must be moved by a process. E. Data cannot move directly from an outside source to a data store. Data must be moved by a process that receives data from the source and places the data into the data store F. Data cannot move directly to an outside sink from a data store. Data must be moved by a process. G. A data store has a noun phrase label. Source/Sink: H. Data cannot move directly from a source to a sink. It must be moved by a process if the data are of any concern to our system. Otherwise, the data flow is not shown on the DFD 1. A source/sink has a noun phrase label. Data Flow: J. A data flow has only one direction of flow between symbols. It may flow in both directions between a process and a data store to show a read before an update. The latter is usually indicated, however, by two separate arrows because these happen at different times. K. A fork in a data flow means that exactly the same data goes from a common location to two or more different processes, data stores, or sources/sinks (this usually indicates different copies of the same data going to different locations). L. A join in a data flow means that exactly the same data come from any of two or more different processes, data stores, or sources/sinks to a common location. M. A data flow cannot go directly back to the same process it leaves. There must be at least one other process that handles the data flow, produces some other data flow, and returns the original data flow to the beginning process. N. A data flow to a data store means update (delete or change). 0. A data flow from a data store means retrieve or use. P. A data flow has a noun phrase label. More than one data flow noun phrase can appear on a single arrow as long as all of the flows on the same arrow move together as one package. (Source: Based on Celko, 1987.) Guidelines for Drawing DFDs In this section, we will consider additional guidelines for drawing DFDs that extend berond the simple mechanics of drawing diagrams and making sure that the rules listed in Tables 7-2 and 7-3 are followed. These guidelines include (1) completeness, (2) consistency, (3) timing considerations, (4) the iterative nature of drawing DFDs, and (5) primitive DFDs. Completeness The concept of DFD completeness refers to whether you have included in your DFDs all of the components necessary for the system you are modeling. If your DFD contains data flows that do not lead anywhere o.
A data flow diagram (DFD) is a graphical representation of the "flow" of data through an information system, modeling its process aspects.
Why DFD technique is so Popular?
Symbols used in DFD
Constructing DFD Models
Data Dictionary
Developing the DFD model of System
Level O DFD or Context Diagram
Level 1 DFD
Strengths of DFD Model
Weaknesses of DFD Model
A graphical tool, useful for communicating with users, managers, and other personnel.
Used to perform structured analysis to determine logical requirements.
Useful for analyzing existing as well as proposed systems.
Focus on the movement of data between external entities and processes, and between processes and data stores.
A relatively simple technique to learn and use.
Data flow diagram is used in software development. It shows the flow of data through the system. It has many levels but beyond level 2 complexity increases. It is used in software engineering, Business analysis, agile development & system structures etc. It can provide a detailed representation of a system. Used as a part of system documentation file. It is very easy to understand. It has many advantages but can make the programmers little confuse concerning the system & take long time to create
A data flow diagram (DFD) illustrates how data is processed by a system in terms of inputs and outputs. As its name indicates its focus is on the flow of information, where data comes from, where it goes and how it gets stored.
Similar to Design Flow Diagram for Information System (20)
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Design Flow Diagram for Information System
1. PROCESS MODELLING : DATA FLOW DIAGRAM
INFORMATION SYSTEM IN CIVIL ENGINEERING | BCA2312 | SEM I 2223
2. LESSON OUTCOMES:
At the end of this chapter students are able to:
Explain the purpose of data-flow diagrams.
Describe the meaning of the symbols used in data-flow diagrams.
Describe the generic framework activities at which data flow diagrams can be used
and the corresponding roles of data-flow diagrams in these stages.
Construct simple data-flow diagrams from a textual description.
Construct a levelled set of data-flow diagrams.
Understand how to check the consistency of related data-flow diagrams.
3. INTRODUCTION TO DATA FLOW DIAGRAM (DFD)
A process model is a formal way of representing how a business operates
Data flow diagramming shows business processes and the data that flows between
them
Logical process models describe processes without suggesting how they are
conducted
Physical models include information about how the processes are implemented
4. INTRODUCTION TO DATA FLOW DIAGRAM (DFD)
What are data-flow diagrams?
Data-flow diagrams (DFDs) model a perspective of the system that is most readily
understood by users – the flow of information through the system and the activities that
process this information.
Data-flow diagrams provide a graphical representation of the system that aims to be
accessible to computer specialist and non-specialist users alike.
The models enable software engineers, customers and users to work together
effectively during the analysis and specification of requirements.
6. INTRODUCTION TO DATA FLOW DIAGRAM (DFD)
The benefits of data-flow diagrams
Data-flow diagrams provide a very important tool for software engineering, for a
number of reasons:
The system scope and boundaries are clearly indicated on the diagrams.
The technique of decomposition of high level data-flow diagrams to a set of more detailed
diagrams, provides an overall view of the complete system, as well as a more
detailed breakdown and description of individual activities, where this is
appropriate, for clarification and understanding.
7. INTRODUCTION TO DATA FLOW DIAGRAM (DFD)
Why Data Flow Diagrams?
Can diagram the organization or the system
Can diagram the current or proposed situation
Can facilitate analysis or design
Provides a good bridge from analysis to design
Facilitates communication with the user at all stages
8. ELEMENTS OF DATA-FLOW DIAGRAMS
Data flow diagram has 4 major elements:
Processes – the main activities that are happening within the system boundary.The process
can be as simple as collecting customer data and storing it in the company database.Also, it
can be a very complicated process such as creating a report containing bank contracts with
customers of all bank clones in a region.
External entities – the sources of information coming to or leaving the system. External
entities are outside systems such as people (customers, stakeholders, managers),
organizations, computers and other systems that send or receive data from our system.
Data stores – places where data is held such as files or repositories.
Data flows – illustrate the movements that data have between the external entities, data
stores, and the processes.
9. ELEMENTS OF DATA-FLOW DIAGRAMS
Data flow diagram has 4 major elements: Symbols used in DFD
ELEMENT SYMBOL
PROCESS
EXTERNAL ENTITIES
DATA STORE
DATA FLOW
Process
Id #
External
Entities /
Source /
Sink
Id #
Process
# Database Name
Data Flow
10. DFD RULES AND GUIDELINE
Creating data flow diagrams requires some guidelines and rules that should be
followed.These guidelines make DFD easily understandable.
1. Each process has at least one outgoing data flow and at least one ingoing data flow.
11. DFD RULES AND GUIDELINE
Creating data flow diagrams requires some guidelines and rules that should be
followed.These guidelines make DFD easily understandable.
2. Each process can go to any other symbol (other processes, data store, and
entities).
12. DFD RULES AND GUIDELINE
Creating data flow diagrams requires some guidelines and rules that should be
followed.These guidelines make DFD easily understandable.
3. Each data store should have at least one incoming and at least one outgoing data
flow.
13. DFD RULES AND GUIDELINE
Creating data flow diagrams requires some guidelines and rules that should be
followed.These guidelines make DFD easily understandable.
4. Entities must be connected to a process by a data flow.
5. Data flows cannot cross with each other.
6. Data stores cannot be connected to external entities. Otherwise, it means you’re
allowing an external entity access to your data files and stores.
7.The labels of processes can be verb phrases. Data stores are displayed by nouns.
8. Data flows cannot run between two external entities without going through a
process.
17. THE DIFFERENT LEVEL OF DFD
There are three main types of data-flow diagram:
Context diagrams — context diagram DFDs are diagrams that present an
overview of the system and its interaction with the rest of the “world”.
Level 0 data-flow diagrams — present a more detailed view of the system than
context diagrams, by showing the main sub-processes and stores of data that make
up the system as a whole.
Level 1 (and lower) data-flow diagrams — Certain elements of any dataflow
diagram can be decomposed (“exploded”) into a more detailed model a level lower
in the hierarchy.
18. THE DIFFERENT LEVEL OF DFD
In a DFD with many levels it’s easy to forget which level you are on.
That’s why each level has different numbering for the processes on the
diagram.The ‘level’ corresponds to the number of decimal places
required to define a process in it. Here’s how it works:
Context Diagram Process labeled “0”
Level 0 Processes labeled 1.0, 2.0, 3.0, .
Level 1 Processes labeled 1.1, 1.2, 1.3, .
Level 2 Processes labeled 1.11, 1.12,...
19. THE DIFFERENT LEVEL OF DFD
There are three main types of data-flow diagram: Course Registration System
Context diagrams — context diagram DFDs are diagrams that present an overview of the
system and its interaction with the rest of the “world”.
Just one process
All sources and sinks that provide
data to or receive data from the process
Major data flows between the process and
all sources/sinks
No data stores
20. THE DIFFERENT LEVEL OF DFD
There are three main types of data-flow diagram:
Level 0 data-flow diagrams — present a more detailed view of the system than context
diagrams, by showing the main sub-processes and stores of data that make
up the system as a whole.
Process is “exploded”
Sources, sinks, and data flows repeated
from context diagram
Process broken down into subprocesses,
numbered sequentially
Lower-level data flows and data stores added
21. THE DIFFERENT LEVEL OF DFD
There are three main types of data-flow diagram:
Level 1 (and lower) data-flow diagrams — Certain elements of any dataflow diagram can be
decomposed (“exploded”) into a more detailed model a level lower in the hierarchy.
“Explode” one process in level 0 diagram.
Break down into lower-level processes,
using numbering scheme
Must include all data flow into and out of
“parent” process in level 0 diagram
Don’t include sources and sinks
May add lower-level data flows and data stores
