Data Flow Diagrams Quiz

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Questions and Answers

What distinct feature helps to identify the level of a Data Flow Diagram (DFD)?

The number of data flows represented

The number of processes it includes

The type of external entities involved

The number of decimal points in the process numbers (correct)

Which DFD level is indicated by process numbers with one decimal point?

Level 0 DFD

Level 2 DFD

Level 1 DFD (correct)

Level 3 DFD

What is the common practice when converting use cases into DFDs?

Rewriting them without any changes

Eliminating external entities

Adding additional process numbers

Combining several smaller data flows into larger ones (correct)

What tool is typically used by project teams to create Data Flow Diagrams?

Process modeling or CASE tools Signup and view all the answers

What is the first step in building a process model with multiple levels of DFDs?

Building a context diagram Signup and view all the answers

Which of the following is a change that may occur when creating DFDs from use cases?

Modifying names of use cases that become processes Signup and view all the answers

What is typically included in a level 2 DFD?

Two decimal points in process numbers Signup and view all the answers

What is the purpose of organizing DFD fragments into a level 0 DFD?

To summarize all process models Signup and view all the answers

What is the purpose of a process model in systems analysis?

To represent how a business system should operate Signup and view all the answers

Which of the following best describes the primary function of a data flow diagram (DFD)?

To depict business processes and data movement Signup and view all the answers

How should a process be named in a data flow diagram?

Starting with a verb and ending with a noun Signup and view all the answers

What characteristic distinguishes a logical process model from a physical model?

Logical models describe processes without suggesting their implementation Signup and view all the answers

What is a key guideline for creating a data flow diagram?

Ensure process names provide clear functional information Signup and view all the answers

Which statement about validating data flow diagrams is true?

Validation checks if diagrams accurately reflect processes and data flows Signup and view all the answers

Which of the following is the correct starting point for creating a DFD?

Understanding the context and scope of the system Signup and view all the answers

What should be the primary concern when designing the layout of a DFD?

Clarity and ease of understanding Signup and view all the answers

What is a characteristic of all data stores in a Data Flow Diagram (DFD)?

They must have at least one input data flow. Signup and view all the answers

Which statement best defines an external entity in the context of a DFD?

A person, organization, or system that interacts with the system. Signup and view all the answers

What does the principle of balancing in DFDs ensure?

Information at one DFD level is consistent with the next level. Signup and view all the answers

What is the function of a context diagram in a DFD?

To present the entire system and its environment. Signup and view all the answers

What is the purpose of decomposing a business process into a hierarchy of DFDs?

To provide more detail at each successive level. Signup and view all the answers

How must children processes of a decomposed parent process behave?

They must completely perform all functions of the parent process. Signup and view all the answers

What best describes the role of external entities in a DFD?

They provide data to and receive data from the system. Signup and view all the answers

Which of the following statements about data flows in a DFD is correct?

Data flows can represent both inputs and outputs for the system. Signup and view all the answers

What is necessary for a data flow to be valid in a data flow diagram?

It must originate or terminate at a process. Signup and view all the answers

What does the context diagram primarily show?

The overall business process as a single system Signup and view all the answers

What describes a 'black hole' in a data flow diagram?

A process that receives data without producing any outputs. Signup and view all the answers

What is the main purpose of the level 0 DFD?

To show all major high-level processes and their interrelations Signup and view all the answers

What is a 'miracle process' in a data flow diagram?

A process that produces a data flow without having any inputs. Signup and view all the answers

What is the issue with Data Flow G if it is depicted as a two-headed arrow?

It is not allowed as data flows should be unidirectional. Signup and view all the answers

How are the processes in the level 1 DFD typically numbered?

Based on the parent process being decomposed Signup and view all the answers

What happens when the context diagram is decomposed?

Details about the data flows inside the system are displayed Signup and view all the answers

What should an analyst assess when encountering Data Store H, which only has inputs?

Confirm that data stored in Data Store H is utilized elsewhere in the process model. Signup and view all the answers

What limits the context diagram's detail?

It omits internal data stores to maintain clarity Signup and view all the answers

How many level 1 DFDs would correspond to a level 0 DFD with three processes?

Three level 1 DFDs corresponding to each process Signup and view all the answers

What term is used to describe processes 2.1, 2.2, and 2.3 in relation to process 2?

Children Signup and view all the answers

Which of the following statements is NOT true about the level 0 DFD?

It represents detailed low-level processes. Signup and view all the answers

What is the primary purpose of developing level 1 DFDs?

To explain the operation of use cases in detail Signup and view all the answers

What typically characterizes a context diagram?

Shows only the primary data flows Signup and view all the answers

Which of the following is NOT a recommended practice when creating a context diagram?

Including excessive detail about every data flow Signup and view all the answers

Which step occurs after developing level 1 DFDs?

Decomposing into level 2 DFDs Signup and view all the answers

What is a key component of the context diagram?

Displaying the relationships with external entities Signup and view all the answers

What happens to inputs and outputs that connect directly to external data stores in a context diagram?

They are omitted from the context diagram Signup and view all the answers

Why might smaller data flows be omitted from the context diagram?

To provide a more simplified and clearer representation Signup and view all the answers

What is the role of external entities in the context diagram?

To connect system processes with outside sources Signup and view all the answers

Study Notes

Systems Analysis and Design Chapter 5: Process Modeling

A process model graphically represents how a business system operates.
It illustrates processes and how data moves among them.
Data Flow Diagrams (DFDs) are a common technique to diagram business processes and the data flowing between them.
They are a logical process model, not a physical one.
Logical models describe processes without showing how they are performed.
Logical models are refined into physical models which provide necessary information for building systems during the design phase.

Chapter 5 Outline

Reading Data Flow Diagrams
Explaining the rules and style guidelines for data flow diagrams
Describing the process used to create data flow diagrams
Validating data flow diagrams

Data Flow Diagram (DFD) Elements

Process: An activity or function within the system.
- Each should have a unique name (verb-noun).
- Perform only one action.
- Have at least one input and one output data flow.
- Have a unique identification number.
Data Flow: A single piece of data or a collection of data.
- Represented as a noun.
- Flows into and out of processes.
- Show input and output data for each process.
- Includes a description of the data elements within it.
Data Store: A collection of data stored in the system.
- Represented by a noun.
- Includes a description.
- Data flows into and out of a data store.
- Indicates information is added to/retrieved from a data store.
External Entity: An external person, organization, or system interacting with the system.
- Represented by a noun.
- Includes a description.
- Data flow to/from a process is related to an external entity.
- Data flows to/from an external entity relate to it.

Using Data Flow Diagrams

Decomposition: Process breakdown into a hierarchy of DFDs for a complex system.
Balancing: Information at one level of a DFD is reflected in the next level.
Context Diagram: Depicts the entire system and its external environment in relation to a single system.
- System's inputs and outputs from/to external entities.
- No data stores within the system are present on the context diagram.
Level 0 (or Level 0 DFD): Shows major high-level processes and their relationships within a system or process.
Level 1 Diagram (or Level 1 DFD): Shows the internal components of a Level 0 process in more detail.
Level 2 Diagram (or Level 2 DFD): Shows further decomposition, describing details of a level 1 DFD.

Creating Data Flow Diagrams

Start with use case information and definitions.
Project teams usually utilize process modeling tools.
Use cases are rewritten as data flow diagrams.
The project team sometimes modifies use case information to conform to data flow diagram rules in terms of names and data flows.
Data flow diagrams are validated for accuracy and completeness. (syntax and semantic errors)

Validating Data Flow Diagrams (DFDs)

Syntax Errors: Structure and usage of diagrams do not adhere to rules. (DFD language conventions).
Semantic Errors: The meaning or logic of the diagram does not accurately describe the process.
Check all data flows for: Unique name, description, connects to at least one process, shown in one direction, & minimum number of crossed lines
Check each process for: Unique name, description, at least one input data flow, at least one output data flow, input/output data flows are different
Check each data store for: Unique name, description, at least one input flow, at least one output flow
Check external entities: Unique name, description, at least one input or output data flow
Context Diagram: One context diagram for the entire system.
Decomposition: Each process is completely described by its children.
Balance: Data flows, stores, & entities on a higher level DFD are on the lower ones.

Holiday Travel Vehicles Example

In the example, the information system modeled is the Holiday Travel Vehicles sales system.
The example shows how to create a context diagram representing the system.
Also how to proceed to creating Level 1 and Level 2 DFDs to detail processes more fully.

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Description

Test your knowledge on Data Flow Diagrams (DFDs) with this quiz. Explore various aspects of DFDs including their levels, conversion from use cases, and best practices for creation. Perfect for students and professionals in systems analysis.