Data Flow Diagrams and Flow Modeling

Vocabulary flashcards covering key terms and concepts related to Data Flow Diagrams (DFDs), flow modeling notation, decomposition practices, and their role in structured design methods as presented in the lecture notes.

Data Flow Diagram (DFD)

A diagrammatic technique that shows how data objects are transformed as they move through a computer-based system.

Flow-Oriented Modeling

An analysis approach that represents the movement and transformation of data within a system, traditionally using DFDs.

External Entity

A producer or consumer of data outside the system boundary, such as a person, device, sensor, or other system.

Process (Bubble)

A transformation step in a DFD that converts input data flows into output data flows to fulfill some system function.

Data Flow

A labeled arrow in a DFD that depicts data in motion from one component to another.

Data Store

A repository shown in a DFD where data is held for later use.

Flow Model

The overall representation of an information transform: inputs enter, are processed, and leave as outputs.

Context Diagram (Level 0 DFD)

The highest-level DFD that shows the entire system as a single process with its external entities and major data flows.

Level 1 DFD

A decomposition of the context diagram that expands the single top-level process into major sub-processes while preserving data flow continuity.

Balancing (Data Flow Continuity)

Ensuring that input and output data flows at one DFD level exactly match those at the next refined level.

DFD Notation

The standardized symbols for external entities (squares), processes (circles/bubbles), data flows (arrows), and data stores (open-ended rectangles).

Process Specification (PSPEC)

A detailed description (narrative, pseudocode, tables, equations, etc.) that defines the algorithm executed by a DFD process.

Decomposition (Leveling)

The iterative breakdown of processes in a DFD into successively finer levels until each can be described with a simple algorithm (typically 3-7 levels deep).

Synchronous Operation

A situation where two processes are directly connected by a data flow, indicating immediate execution dependency.

Asynchronous Operation

A situation where processes communicate via a data store, meaning execution is decoupled in time.

Transform Flow

A DFD characteristic in which data flows from input, through a transform center, to output—often mapped by structured design.

Transaction Flow

A DFD pattern where a single incoming data item (transaction) can trigger one of many possible paths through the system.

Transform Center

The portion of a DFD where incoming data is converted into outgoing data; isolated when mapping to program structure.

Flow Boundary

The demarcation between incoming raw data flow and outgoing processed data flow in a transform-flow DFD.

Structured Design

A data-flow-oriented design technique that maps DFD elements into a hierarchical program architecture through systematic steps.

First-Level Factoring

Initial partitioning of the program structure derived from a DFD, separating major transform components and control modules.

Second-Level Factoring

Further refinement of program structure after first-level factoring, enhancing modularity and adherence to design heuristics.