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Difference Between DFD and ERD
DFD (Data Flow Diagram) and ERD (Entity Relationship Diagram) are two types of diagrams that are used to describe the flow of data and information within a system. DFD is used to model data flow between processes, data stores, and external entities. ERD is a graphical representation of entities and their relationships.
Read this article to find out more about DFD and ERD and how they are different from each other.
What is DFD?
DFD consists of four parts: entities, processes, data flows, and data stores. Customers, suppliers, and employees are examples of entities that are external data sources or destinations. The actions or tasks that transform data into useful information are known as processes. Data flows are the pathways that data takes as it moves through the system, whereas data stores are places where data is stored for later use.
DFD is a hierarchical diagram, with each level providing a more thorough perspective of the system. Level 0, the top level of DFD, provides an overview of the system, displaying the primary processes and data flows. As the diagram moves to a lower level, more detail is added, revealing the processes and data flows in more detail.
Context Diagram, Level 0 DFD, Level 1 DFD, and so on are examples of DFDs that can be used to model various parts of a system. The highest-level DFD is a Context Diagram, which shows the system as a single process with input and output data flows. The first level of decomposition is Level 0 DFD, which separates the single process into its principal subprocesses. Level 1 DFD expands on the processes of Level 0, breaking them down into more complex subprocesses, and so on.
DFD can be used for a variety of applications, including system analysis, design, and documentation. It shows the system in a simple and understandable way, helping stakeholders understand the flow of data and identify possible issues or improvements.
What is ERD?
ERD is a graphical representation of entities and their relationships. It is used to model a database's structure as well as the relationships between the entities that comprise that structure. Entities, attributes, and relationships make up ERD. Entities are objects or concepts in a system; attributes explain their properties; and relationships describe their relationships. ERD helps in the visualisation of the data model and its relationships, which helps in the identification of potential data quality issues and ensuring the preservation of data integrity.
The basic components of an ERD are −
Entities − An entity is an easily identified and described object or concept within a system. In an ERD, entities are represented by rectangles.
Attributes − An attribute is a characteristic or property of an entity. It is represented by an oval shape connected to an entity.
Relationships − A relationship is a connection formed by multiple entities. In an ERD, it is represented by a line connecting the two entities.
Cardinality − An entity is easily identified and described. Cardinality is the number of instances of one entity that can be connected with another. It can be represented by symbols such as "one," "many," or "zero" on the lines connecting entities in an ERD.
An entity is easily identified and described. ERD can be used to model any type of database system, from simple to complex. The following are the steps to creating an ERD −
Identify the entities − An entity is easily identified and described. The first step to creating an ERD is to identify the entities in the system under consideration. These entities represent the system's objects or concepts.
Identify the attributes − Following the identification of the entities, the next step is to identify the attributes or properties of each entity. These attributes contribute to an understanding of each entity's characteristics.
Identify the relationships − After identifying the entities and their attributes, the next step is to determine the relationships between the entities. This involves determining the relationships between the entities and their cardinality.
Draw the ERD − An entity is easily identified and described. Finally, the ERD can be created by representing the entities as rectangles, the attributes as ovals related to the entities, and the connections as lines connecting the entities with the proper cardinality symbols.
ERD is a valuable database design technique because it helps to assure data accuracy and integrity by recognizing potential data quality concerns and ensuring that entity connections are appropriately defined.
Difference between DFD and ERD
The following table highlights the major differences between DFD and ERD −
Characteristics |
DFD |
ERD |
|---|---|---|
Components |
Entities, processes, data flows, and data stores |
Entities, attributes, relationships, and cardinality |
Diagram elements |
Squares, rectangles, circles, and arrows |
Rectangles, ovals, lines, and symbols |
Focus |
System's data flow and processing |
Database's structure and relationships |
Usage |
It is used in software engineering, business analysis, and system design |
It is used in database design, development, and system analysis |
Example scenario |
Modeling an online ordering system |
Designing a customer database for a retail store |
Representation |
Graphical representation of the flow of data |
Graphical representation of entities and their relationships |
Scope |
Can model any type of system, from simple to complex |
Limited to modeling database structures |
Conclusion
In conclusion, DFD and ERD are both useful tools for modelling data and information flow within a system. While DFD represents the flow of data between processes, data stores, and external entities, ERD models the structure of a database and the relationships between the entities that comprise that structure.
Understanding the differences between these two types of diagrams will help developers and analysts select the best tool for their specific needs and ensure the accuracy and integrity of their data.
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