1. Data Flow Diagram (DFD) :
Data means information, flow means to move, and diagram means a picture to represent something. So, DFD is simply the graphical representation of the flow of data or information. It is a framework or pattern of the data systems. It includes data input, data output, storing data. DFD describes the process of taking the data as input, storing the data, giving the data as output. DGD describes the path of data that completes the process.
There are mainly two types of DFD: Physical Data Flow Diagram, and Logical Data Flow Diagram.
Example of DFD – Lemonade Stand
2. Entity Relationship Diagram (ERD) :
ERD is also known as the Entity-Relationship Model. ERD was originally proposed by Peter Chen. Entity means any object used to store information and are distinguishable, relationship means connection, and diagram/model means a picture uses to represent something. So, ERD is simply the diagram or model that is used to represent or show the relationship between the entities or data objects that are stored in a database. The main components of the E-R model are an entity, attributes, and relationship. It is a very easy way to represent the database design.
Example of ERD – School Information Management
Difference between DFD and ERD :
|1.||It stands for Data Flow Diagram.||It stands for Entity Relationship Diagram or Model.|
|2.||Main objective is to represent the processes and data flow between them.||Main objective is to represent the data object or entity and relationship between them.|
|3.||It explains the flow and process of data input, data output, and storing data.||It explains and represent the relationship between entities stored in a database.|
|4.||Symbols used in DFD are: rectangles (represent the data entity), circles (represent the process), arrows (represent the flow of data), ovals or parallel lines (represent data storing).||Symbols used in ERD are: rectangles (represent the entity), diamond boxes (represent relationship), lines and standard notations (represent cardinality).|
|5.||Rule followed by DFD is that at least one data flow should be there entering into and leaving the process or store.||Rule followed by ERD is that all entities must represent the set of similar things.|
|6.||It models the flow of data through a system.||It model entities like people, objects, places and events for which data is stored in a system.|
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