Questions and Answers
What is the main difference between a context diagram and a Level 1 DFD?
What does the 'D' symbol represent in a Level 1 DFD?
Why is it important to draw separate external entities for each role in a system?
What is the purpose of drawing both positive and negative cases in a system?
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What is the symbol used to illustrate an external entity in a Level 1 DFD?
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What is the purpose of a Level 1 DFD in system design?
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What is the primary purpose of identifying external entities in a system?
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When drawing a Level 1 DFD, what assumption should be made about a person's role?
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What can be considered a data store?
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What is the difference between a 'T' and an 'M' symbol in a Level 1 DFD?
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What is a characteristic of a process in a system?
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What is a rule for data flow in a system?
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What is a requirement for every process in a system?
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What is a requirement for every data store in a system?
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What is a rule for linking processes in a system?
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What is not allowed in a data flow diagram?
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What is the primary purpose of creating a requirements specification document in SSADM?
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What type of diagram is used to show the flow of data between different system entities?
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What is the highest level of modeling in Data Flow Diagrams (DFDs)?
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What is the purpose of a Context Diagram in Data Flow Diagrams (DFDs)?
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What is NOT a type of illustration or plan used in Logical Design?
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What is an entity in the context of software development?
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How many types of Data Flow Diagrams (DFDs) can be listed?
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What is the purpose of Logical Design in the development of an information system?
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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.