Chapter 5

Vocabulary flashcards created from Chapter 5 Data and Process Modeling notes covering key terminology, DFD symbols, dictionary entries, control structures, and model types.

Logical Model

A model that shows what an information system must do, regardless of how it will be implemented physically.

Physical Model

A model that describes how an information system will be constructed and physically implemented.

Data Flow Diagram (DFD)

A graphical model that uses various symbols to show how an information system transforms input data into useful information without showing program logic or processing steps.

Gane and Sarson Symbol Set

A popular set of symbols used in data flow diagrams where processes are drawn as rounded rectangles, data stores as flat open rectangles, data flows as arrows, and external entities as shaded rectangles.

Process Symbol

A symbol in a DFD that transforms input data into output data using business logic; it must contain at least one input and at least one output.

Black Box

A metaphor for a process symbol in a DFD whose internal processing details are hidden from view.

Data Flow Symbol

A line with a single or double arrowhead in a DFD representing one or more data items moving between processes, data stores, or external entities.

Spontaneous Generation

An error in a DFD process symbol where a process produces output data without receiving any input data.

Black Hole

An error in a DFD process symbol where a process receives input data but produces no output data.

Gray Hole

An error in a DFD process symbol where a process receives input data that is obviously unable or insufficient to produce the given output data.

Data Store Symbol

A symbol in a DFD representing data that the system stores for later use; it must be connected to a process with a data flow.

External Entity

A person, department, outside organization, or other system that interfaces with an information system by sending data to it or receiving output from it.

Terminator

Another name for an external entity in a DFD because it marks a data origin or final destination.

Context Diagram

A top-level data flow diagram that provides an overview of the system by placing the entire information system into a single process symbol (Process 0) surrounded by external entities.

Diagram 0

An exploded view of Process 0 from the context diagram that shows the system's major processes, data flows, data stores, and external entities.

Parent Diagram

A higher-level DFD that contains a process symbol that is exploded or decomposed into a more detailed lower-level diagram.

Child Diagram

A detailed lower-level DFD that shows the breakdown of a single process from a parent diagram.

Leveling

The process of drawing a series of increasingly detailed DFDs (also called exploding or partitioning) to describe an information system from a general overview down to specific details.

Balancing

A modeling technique that ensures the input and output data flows of a child DFD match exactly with the inputs and outputs of its parent process.

Data Dictionary

A central storehouse or repository of information about a system's data that defines and describes all data elements, records, data flows, data stores, processes, and entities.

Data Element

The smallest piece of data that has meaning within an information system, also referred to as a field or data item.

Record

A meaningful combination of related data elements that is included in a data flow or retained in a data store, also called a data structure.

Alias

An alternative name for a data element or data store documented within the data dictionary.

Domain

The set of acceptable values and validity rules permitted for a given data element in a data dictionary.

Process Description

Documentation of the functional primitive details, representing a specific set of processing steps and business logic using structured English, decision tables, or decision trees.

Functional Primitive

A process in a DFD that consists of a single function and cannot be exploded or decomposed any further.

Modular Design

A design approach based on combinations of three logical control structures—sequence, selection, and iteration—that serve as building blocks for process logic.

Sequence Control Structure

A logical structure in modular design where processing steps are executed one after another in a fixed order.

Selection Control Structure

A logical structure in modular design that executes one of two or more alternative pathways based on the evaluation of a condition.

Iteration Control Structure

A logical structure in modular design (also known as looping) that repeatedly executes one or more processing steps until a specific condition is met.

Structured English

A process description tool that uses a restricted vocabulary and the three logical structures (sequence, selection, iteration) with indentation to clearly describe processing logic.

Decision Table

A tabular process description tool that shows all possible combinations of conditions, rules, and resulting actions to describe complex logic.

Decision Tree

A graphical process description tool that displays conditions, actions, and rules in a horizontal tree structure.

Four-Model Approach

A modeling sequence in systems analysis that involves developing a physical model of the current system, a logical model of the current system, a logical model of the new system, and a physical model of the new system.