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Definition

Systems Design

Definition

Systems design is simple the design of systems. It implies a systematic and rigorous approach to design -- an approach demanded by the scale and complexity of many system problems.

Is the third of the five stages of Systems Development Life Cycle (SDLC).

Definition

To develop a logical model of the system and considered various development strategies.

To create a blueprint that will satisfy all documented requirements for the system. At this stage, the user interface will be designed and all the necessary outputs, inputs, and processes will be identified.

Definition

Flowchart

Definition

A flow chart is a graphical or symbolic representation -- This diagrammatic representation can give a step-by-step solution to a given problem -- of a process, showing the steps as boxes of various kinds, and their order by connecting these with arrows.

Definition

Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.

Each step in the process is represented by a different symbol and contains a short description of the process step. All processes should flow from top to bottom and left to right.

Symbols

Flowchart

Start and End symbol

Represented as circles, ovals or rounded rectangles, usually containing the word "Start" or "End", or another phrase signaling the start or end of a process, such as "submit enquiry" or "receive product".

Start

End

Arrow Symbol

Showing "flow of control".

An arrow coming from one symbol and ending at another symbol represents that control passes to the symbol the arrow points to.

Generic Processing Symbol

Represented as rectangles.

Denotes the process to be carried out

Examples: "Add 1 to X"; "replace identified part"; "save changes" or similar.

Add 1 to X

Save changes

Input/Output Symbol

Represented as a parallelogram.

Denotes an input operation or output operation.

Examples: Get X from the user; display X.

Display X

Get X

Conditional or Decision Symbol Represented as a

diamond showing where a decision is necessary, commonly a Yes/No question or True/False test.

The conditional symbol is peculiar in that it has two arrows coming out of it, usually from the bottom point and right point, one corresponding to Yes or True, No or False.

Is x => 10?

Yes

No

Labeled connectors

Represented by an identifying label inside a circle.

Labeled connectors are used in complex or multi-sheet diagrams to substitute for arrows.

A

A

Types

Flowchart

Types

Document flowcharts Showing controls over a document-flow

through a system

Data flowcharts Showing controls over a data flows in a

system

Types

System flowcharts Showing controls at a physical or

resource level

Program flowchart Showing the controls in a program within

a system

Types

High-Level Flowchart

A high-level (also called first-level or top-down) flowchart shows the major steps in a process.

It illustrates a "birds-eye view" of a process.

It can also include the intermediate outputs of each step (the product or service produced), and the sub-steps involved.

Types

Detailed Flowchart

The detailed flowchart provides a detailed picture of a process by mapping all of the steps and activities that occur in the process.

This type of flowchart indicates the steps or activities of a process and includes such things as decision points, waiting periods, tasks that frequently must be redone (rework), and feedback loops.

Types

Deployment or Matrix Flowchart

A deployment flowchart maps out the process in terms of who is doing the steps.

It is in the form of a matrix, showing the various participants and the flow of steps among these participants.

It is chiefly useful in identifying who is providing inputs or services to whom, as well as areas where different people may be needlessly doing the same task.

Introduction

Data Flow Diagram

Definition

Data Flow Diagram (DFD) is a graphical representation of the "flow" of data through an information system, modeling its process aspects.

DFDs can also be used for the visualization of data processing (structured design).

Definition

Often they are a preliminary step used to create an overview of the system which can later be elaborated.

A DFD shows what kinds of data will be input to and output from the system, where the data will come from and go to, and where the data will be stored.

Definition

It does not show information about the timing of processes, or information about whether processes will operate in sequence or in parallel.

Symbols

Data Flow Diagram

Symbols

Introduction

Context Diagram

Definition

In software engineering and systems engineering, a Context Diagram is a diagram that represents the actors outside a system that could interact with that system.

Definition

A context diagram is a data flow diagram, with only one massive central process that subsumes everything inside the scope of the system.

It shows how the system will receive and send data flows to the external entities involved.

Definition

Context Diagram is the highest level view of a system.

Context Diagrams shows a system, often software-based, as a whole and its inputs and outputs from/to external factors.

It is similar to a Block diagram.

Introduction

Gantt Chart

Definition

A Gantt chart is a graphical representation of the duration of tasks against the progression of time.

A Gantt chart is a useful tool for planning and scheduling projects.

Gantt charts illustrate the start and finish dates of the terminal elements and summary elements of a project.

Definition

Terminal elements and summary elements comprise the work breakdown structure of the project.

Some Gantt charts also show the dependency relationships between activities.

A Gantt chart is a horizontal bar chart developed as a production control tool in 1917 by Henry L. Gantt, an American engineer and social scientist.