Data Flow Diagrams (DFDs) Level 1

Questions and Answers

What is the main difference between a context diagram and a Level 1 DFD?

The number of external entities depicted

The type of symbols used to represent processes

The number of data stores shown

The level of detail in illustrating internal mechanisms (correct)

What does the 'D' symbol represent in a Level 1 DFD?

External entity

Manual data store

Digital data store (correct)

Temporary data store

Why is it important to draw separate external entities for each role in a system?

To show data flows between external entities

To illustrate internal mechanisms

To reduce the number of external entities

To avoid confusion and ensure clarity (correct)

What is the purpose of drawing both positive and negative cases in a system?

To consider all possible scenarios and outcomes Signup and view all the answers

What is the symbol used to illustrate an external entity in a Level 1 DFD?

Ellipse Signup and view all the answers

What is the purpose of a Level 1 DFD in system design?

To detail internal mechanisms and data flows Signup and view all the answers

What is the primary purpose of identifying external entities in a system?

To initiate a process Signup and view all the answers

When drawing a Level 1 DFD, what assumption should be made about a person's role?

A person can have one or more roles Signup and view all the answers

What can be considered a data store?

Any type of data storage, including paper-based records Signup and view all the answers

What is the difference between a 'T' and an 'M' symbol in a Level 1 DFD?

T represents a temporary data store, while M represents a manual data store Signup and view all the answers

What is a characteristic of a process in a system?

It is an action done by an internal personnel or subsystem Signup and view all the answers

What is a rule for data flow in a system?

Data flow must be from an entity to a process or a process to an entity Signup and view all the answers

What is a requirement for every process in a system?

It must have at least one input data flow and one output data flow Signup and view all the answers

What is a requirement for every data store in a system?

It must have at least one input data flow and one output data flow Signup and view all the answers

What is a rule for linking processes in a system?

All processes must be linked to at least one data store or another process Signup and view all the answers

What is not allowed in a data flow diagram?

Two data flows crossing each other Signup and view all the answers

What is the primary purpose of creating a requirements specification document in SSADM?

To communicate between different stakeholders within the development process Signup and view all the answers

What type of diagram is used to show the flow of data between different system entities?

Data Flow Diagram (DFD) Signup and view all the answers

What is the highest level of modeling in Data Flow Diagrams (DFDs)?

Level 0 DFD (Context Diagrams) Signup and view all the answers

What is the purpose of a Context Diagram in Data Flow Diagrams (DFDs)?

To show data flows between the system and external entities only Signup and view all the answers

What is NOT a type of illustration or plan used in Logical Design?

Requirements Specification Signup and view all the answers

What is an entity in the context of software development?

Anything including human, place, vehicle, animal or another system Signup and view all the answers

How many types of Data Flow Diagrams (DFDs) can be listed?

2 Signup and view all the answers

What is the purpose of Logical Design in the development of an information system?

To make plans and high-level illustrations of the system Signup and view all the answers

Study Notes

Data Flow Diagrams (DFDs)

DFDs are used to show the flow of data between different system entities.
Entities in software development can be humans, places, vehicles, animals, or other systems.

Level 1 DFD

Used to illustrate internal mechanisms as well as external entity data flows.
More in-detailed than context diagrams.
Uses different symbols from context diagrams.

Symbols Used in Level 1 DFD

To illustrate a process
To illustrate a data store (types: digital, manual, temporary)
To illustrate an external entity
To show data flows between the considering system and external entities
To show data flows between external entities

Steps to Create Level 1 DFD

Care about internal processes, data stores, data flows, and external entities.
Find external entities first, as an entity only initiates a process.
A process is an action done by an internal personnel or internal subsystem.
A data store can be any type of data store (e.g., table written on paper).

Level 1 DFD Rules

Data cannot flow between two entities.
Data flow must be from entity to a process or a process to an entity.
Data cannot flow between two data stores.
Data flow must be from data store to a process or a process to a data store.
Data cannot flow directly from an entity to a data store.
A process must have at least one input data flow and one output data flow.
Every process must have input data flow to process the data and an output data flow for the processed data.
A data store must have at least one input data flow and one output data flow.
Every data store must have input data flow to store the data and an output data flow for the retrieved data.
Two data flows cannot cross each other.
All processes in the system must be linked to at least one data store or another process.

Requirements Specification

A crucial document outlining functional and non-functional requirements of the proposed information system in SSADM.
Includes functional requirements, non-functional requirements, constraints, assumptions and dependencies, etc.
The documentation process is the standard communication medium between different stakeholders within the development process.

Logical Design

Includes making plans and high-level illustrations (modeling) in software development.
Examples include data flow diagrams, document flow diagrams, activity diagrams, flow charts, class diagrams, etc.

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Description

Learn about Data Flow Diagrams (DFDs) and their application in software development. Understand Level 1 DFDs, their symbols, and how they illustrate data flows between entities.