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Design Flow Diagram for Information System

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.

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PROCESS MODELLING : DATA FLOW DIAGRAM INFORMATION SYSTEM IN CIVIL ENGINEERING | BCA2312 | SEM I 2223
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.
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
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.
INTRODUCTION TO DATA FLOW DIAGRAM (DFD)  Example of DFD
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.
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
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.
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
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.
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).
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.
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.
DFD RULES AND GUIDELINE  Summary
COMMON DFD MISTAKES  Summary
COMMON DFD MISTAKES
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.
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,...
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
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
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
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