ICT Comparison ERD and DFD

Comparison of Entity-Relationship Diagram (ERD) and Data Flow Diagram (DFD)

Entity-Relationship Diagrams (ERD) and Data Flow Diagrams (DFD) are both widely used in system analysis and design, but they serve different purposes and represent different aspects of the system.

Aspect	Entity-Relationship Diagram (ERD)	Data Flow Diagram (DFD)
Purpose	Describes the data and relationships between entities in a system.	Describes the flow of data and the processes that transform the data.
Focus	Data structure and relationships.	Data processes and movement.
Type of Diagram	Static diagram.	Dynamic diagram.
Representation	Entities (represented as rectangles), relationships (represented as diamonds), attributes (represented as ovals).	Processes (represented as circles or rectangles), data flows (represented as arrows), data stores (represented as open-ended rectangles), external entities (represented as squares).
Primary Concern	The structure of the system's data.	The flow and processing of data within the system.
Level of Detail	Typically shows high-level entities and relationships; does not show processes or workflows.	Often shows multiple levels of abstraction (context-level DFD, child DFDs).
Focus Area	Entities (e.g., Customers, Orders), their attributes, and relationships (e.g., one-to-many, many-to-many).	Processes (e.g., Order Processing, Inventory Management), data flows, and interactions between entities and systems.
Use Case	Used to model the data structure of a system, often in database design.	Used to model the data flow and processes of a system, especially in system or software design.
Best Suited For	Conceptualizing databases, designing relational databases, and representing business rules.	Representing business processes, understanding system requirements, and defining how data moves through a system.
Level of Abstraction	More abstract, focusing on "what" data exists and "how" it's related.	Focuses on "how" data flows and is processed within the system.
Tools Used	Often used in Database Design tools like ERwin, Microsoft Visio, or UML.	Often used in process modeling tools or software like Microsoft Visio, Lucidchart, or structured analysis methods.
Example	Entities: Customer, Order; Relationships: Customer places Order.	Process: Order Processing, Data Flow: Order Data, External Entity: Customer.