Data Flow Diagram Notation

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Questions and Answers

What is the purpose of a report generator in a data-flow diagram?

To create a data dictionary for the system
To create a structured chart for the system
To design a pseudo-code for the system
To generate a report describing all named entities in the diagram (correct)

What is listed in a data dictionary?

All data elements appearing in the DFD model of a system (correct)
Only the names of the data stores
Only data flows in the system
Only composite data elements

What is the significance of a data dictionary in software development?

It is not essential for software development
It is used to create a structured chart for the system
It is only used for small projects
It provides a means to determine the definition of various data structures (correct)

What does a data dictionary entry contain?

The objective and definition of the data item (C)

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What is the benefit of a data dictionary in a software development project?

It provides a standard language for all relevant information (D)

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What is the main purpose of a structured chart?

To partition a system into block boxes (A)

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What is the objective of the report generator?

To find all the names used in the data-flow diagram (C)

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What is contained in the data dictionary for the smallest units of data elements?

The name and type of the data item (D)

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What is the primary purpose of a Structured Chart?

To show the system partitions into modules (C)

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What is the main difference between pseudo-code and programming languages?

Pseudo-code avoids variable declaration (C)

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What does an Entity-Relationship model represent?

The relationship between entities and their attributes (A)

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What is the purpose of a Data Flow Diagram?

To show the flow of data through a system (A)

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What is a characteristic of a Black box system?

The user has no knowledge of the internal design (B)

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What is the main purpose of a Data Dictionary?

To define the attributes and their domains (C)

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What is the primary advantage of using pseudo-code?

It provides a method to perform a task (C)

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What is the purpose of a Structured Chart in software design?

To represent the system's functionality and its internal design (B)

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What is the term used to describe the logical association among entities?

Relationship (A)

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What type of mapping cardinality is used to describe a situation where one entity is associated with multiple other entities?

One to many (B)

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In object-oriented design, what is the term used to describe the distribution of state among objects?

Encapsulation (D)

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What is the term used to describe a group of similar objects in object-oriented design?

Class (D)

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What is the purpose of message passing in object-oriented design?

To enable objects to communicate with each other (A)

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What is the term used to describe the complexity handling technique in object-oriented design?

Abstraction (C)

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What is the term used to describe a procedure or function call in object-oriented design?

Message (B)

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What is the term used to describe the instance of a class in object-oriented design?

Object (A)

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Study Notes

Data-Flow Diagram Entities

Data-flow diagram entities use different icons to represent data-flow diagrams, but their meanings are similar
A report generator produces a report that describes all named entities in a data-flow diagram
The report generator finds names used in the data-flow diagram, looks up a data dictionary, and retrieves information about each name

Data Dictionaries

A data dictionary lists all data elements appearing in a Data-Flow Diagram (DFD) model of a system
It contains data flows, contents of data stores, objectives of data items, and definitions of composite data elements
Each data dictionary entry lists the name, type, and definition of data elements
A data dictionary provides a standard language for engineers working on a project, ensuring consistent vocabulary for data items
It helps determine definitions of data structures in terms of their component elements

Structured Charts

A structured chart partitions a system into block boxes, showing:
- System partitions into modules
- Hierarchy of component modules
- Relations between processing modules
- Interaction between modules
- Information passed between modules
Structured charts use specific notations to represent these concepts

Pseudo-Code

Pseudo-code is written in a programming language style, with comments and descriptions
It avoids variable declarations, using actual programming language constructs (e.g., C, Fortran, Pascal)
Pseudo-code provides a method to perform a task, as if a computer is executing the code
It contains more programming details than Structured English

Entity-Relationship Model

Entity-Relationship (ER) model is a type of database model based on real-world entities and relationships
ER Model creates a set of entities with attributes, constraints, and relations
An entity is a real-world being with properties (attributes) and a set of values (domain)
Relationships among entities are mapped with entities in various ways, with mapping cardinalities (one-to-one, one-to-many, many-to-one, many-to-many)

Object-Oriented Design

In object-oriented design, a system is viewed as a collection of objects (entities)
Each object handles its state data, and tasks defined for one object cannot refer or change data of other objects
Objects are instances of a class, and classes may inherit features from a superclass
Key terms in object-oriented design include:
- Objects: entities involved in the solution design
- Classes: generalized descriptions of objects
- Messages: objects communicate by message passing