structured analysis and structured designdslab.konkuk.ac.kr/class/2019/19se/lecture note... ·...

Structured Analysis and Structured Design

- Introduction to SASD- Structured Analysis- Structured Design

Lecturer: JUNBEOM [email protected]

http://dslab.konkuk.ac.krVer. 1.5

SASD Process

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Activity

Time

Statement of Purpose

System Context Diagram

Event List

Data Dictionary

ERD

DFD

Process Specification

State Transition Diagram

Structured Chart

Environmental Model

Behavioral Model

Implementation Model


• A clear and concise textual description of the purpose for the system to develop

• It should be deliberately vague.

• It is intended for top level management, user management and others who are not directly involved in the system.

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• Highlights the boundary between the system and outside world.

• Highlights the people, organizations and outside systems that interact with the system under development.

• A special case of DFD

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System Context Diagram - Notation

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Process : represents the proposed system

Terminator : represents the external entities

Flow : represents the in/out data flows

System Context Diagram – RVC Example

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RVC Control

Sensor

Motor

Cleaner

Event List

• A list of the event/stimuli outside of the system to which it must respond.

• Used to describe the context diagram in details.

• Types of events

– Flow-oriented event : triggered by incoming data

– Temporal event : triggered by internal clock

– Control event : triggered by an external unpredictable event

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Event List – RVC Example

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Input/ Output Event Description

Front Sensor Input Detects obstacles in front of the RVC

Left Sensor Input Detects obstacles in the left side of the RVC periodically

Right Sensor Input Detects obstacles in the right side of the RVC periodically

Dust Sensor Input Detects dust on the floor periodically

DirectionDirection commands to the motor (go forward / turn left with an angle / turn right with an angle)

Clean Turn off / Turn on / Power-Up

Context Diagram for RVC

System Context Diagram – RVC Example

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RVC Control

Sensor

Motor

Cleaner

Front Sensor InputLeft Sensor InputRight Sensor InputDust Sensor Input

Direction

Clean

Data Flow Diagram (DFD)

• Provides a means for functional decomposition.

• Composed of hierarchies(levels) of DFDs.

• Notation (A kind of CDFD)

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Data Process

Control Process

Terminator

Data Store

Data Flow

Control Flow

DFD Level 0 – RVC Example


RVC Control

0

Front Sensor Motor

Cleaner

Direction

Clean

Left Sensor

Right Sensor

Dust Sensor

Front Sensor Input

Left Sensor Input

Right Sensor Input

Dust Sensor Input

Digital Clock

Tick



Input/ Output Event

Description Format / Type

Front Sensor Input Detects obstacles in front of the RVC True / False , Interrupt

Left Sensor Input Detects obstacles in the left side of the RVC periodically True / False , Periodic

Right Sensor Input Detects obstacles in the right side of the RVC periodically True / False , Periodic

Dust Sensor Input Detects dust on the floor periodically True / False , Periodic

DirectionDirection commands to the motor (go forward / turn left with an angle / turn right with an angle)

Forward / Left / Right / Stop

Clean Turn off / Turn on / Power-Up On / Off / Up

(A kind of) Data Dictionary



Obstacle & Dust

Detection1

Front Sensor Input

Left Sensor Input

Right Sensor Input

Dust Sensor Input

Tick

Obstacle & DustLocation

Cleaner & MotorControl

2

Direction

Clean



DetermineObstacleLocation

1.5

Front Sensor Input

Left Sensor Input

Right Sensor Input

Dust Sensor Input

Tick

ObstacleLocation

Front Sensor

Interface1.1

LeftSensor

Interface1.2

RightSensor

Interface1.3

DustSensor

Interface1.4

Tick

Tick

Front Obstacle

Left Obstacle

Right Obstacle

DetermineDust

Existence1.6

Dust Existence

DustExistence



ObstacleLocation

DustExistence

Main Control

2.1

Motor Command

Cleaner Command

MotorInterface

2.2

CleanerInterface

2.3

Tick

Direction

Clean



ObstacleLocation

DustExistence

Controller2.1.1

Motor Command

Cleaner Command

TickMove

Forward2.1.2

Turn Left2.1.3

Turn Right2.1.4

Motor Command

Motor Command

Enable

Disable

Trigger

TriggerTick

Tick



Move Forward

Turn RightTurn Left

/ Enable “Move Forward”, Cleaner Command (On)

Tick [F && !R]/ Disable “Move Forward”, Cleaner Command (Off),Trigger “Turn Right”

Tick / Enable “Move Forward”, Cleaner Command (On)

Tick [F && !L]/ Disable “Move Forward”, Cleaner Command (Off),Trigger “Turn Left”

Tick / Enable “Move Forward”, Cleaner Command (On)

Stop

Tick [F && L && R]/ Disable “Move Forward”, Cleaner Command (Off),

Many problems in this model:1. “Stop” state2. Do not consider “Dust”3. …

State Transition Diagram for Controller 2.1.1

DFD – RVC Example


Process Specification

• Shows process details which are implied but not shown in a DFD.

• Specifies the input, output, and algorithm of a module in a DFD.

• Normally written in pseudo-code or table format.

• Example – “Apply Payment”

For all payments

If payment is to be applied today or earlier and has not yet been applied

Read account

Read amount

Add amount to account’s open to buy

Add amount to account’s balance

Update payment as applied


Zhou Qun, Kendra Hamilton, and Ibrahim Jadalowen (2002)

Process Specification – RVC Example


Reference No. 1.2

Name Left Sensor Interface

Input Left Sensor Input (+Data structure if possible) , Tick

Output Left Obstacle (+Data structure)

Process Description“Left Sensor Input” process reads a analog value of the left sensorperiodically, converts it into a digital value such as True/False, andassigns it into output variable “Left Obstacle.”

Data Dictionary

• Defines data elements to avoid different interpretations.

• Not used widely in recent years.

• Example [Yourdon 1989]

A: What’s a name?

B: Well, you know, it’s just a name. It’s what we call each other.

A: Does that mean you can call them something different when you are angry or happy?

B: No, of course not. A name is the same all the time.

A: Now I understand. My name is 3.141592653.

B: Oh your name is PI…But that’s a number, not a name. But what about your first and last name. Or, is your first name 3 and your last name 141592653?


Data Dictionary

• Example– Element Name = Card Number

– Definition = *Uniquely identifies a card*

– Alias = None

– Format = LD+LD+LD+LD+SP+LD+LD+LD+LD+SP+ LD+LD+LD+LD+SP+LD+LD+LD+LD

– SP = “ ” *Space*

– LD = {0-9} *Legal Digits*

– Range = 5191 0000 0000 0000 ~ 5191 9999 9999 9999


State Transition Diagram

• Shows the time ordering between processes.

• More primitive than the Statechart diagram in UML.

• Different from the State transition diagram used in DFD.

• Not widely used.

• Notation


TransitionsObjects

State Transition Diagram - Example


Structure Charts

• Structured Design (SD)

• Functional decomposition (Divide and Conquer)

– Information hiding

– Modularity

– Low coupling

– High internal cohesion

• Needs a transform analysis.


Structured Charts – Transform Analysis


Afferent Flow(Input)

Efferent Flow(Output)

Central Transformation(Control)

Structured Charts – Transform Analysis


Input(Afferent Flow)

Process(Central Transformation)

Output(Efferent Flow)

Control

ProcessInput Output

Structured Charts – Notation


Modules

Library modules

Module call

Data Flow

Control Flow

Basic Notation [Yourdon 1989]

Asynchronous module call

Data module

Iteration

Decision

Variations

Structured Charts – RVC Example (Basic)


DetermineObstacle Location

Determine Dust Existence

Controller

Front SensorInterface

Left SensorInterface

Right SensorInterface

Dust SensorInterface

Move Forward Turn Left Turn Right

Main

Obstacle Location Dust Existence

EnableDisable

Trigger Trigger

Structured Charts – RVC Example (Advanced)


DetermineObstacle Location

Determine Dust Existence

Controller

Front SensorInterface

Left SensorInterface

Right SensorInterface

Dust SensorInterface

Move Forward Turn Left Turn Right

Main

Obstacle Location

Dust Existence

EnableDisable

Trigger

Trigger

Summary

• SASD is a process-driven software analysis technique.

• SASD has a long history in the industry and it is very mature.

• It provides a good documentation for requirements.

• In recent years, it is widely used for developing real-time embedded system’s software.


SASD

What is a good analysis & design?

• There are no explicit criteria for analysis & design

• The judgement of analyst & designer is a key of design– System context and event analysis

– DFD divide and design

– Behavior analysis for state transition diagram




Simple Vending Machine (SVM)

- A vending machine sells two beverages.- It reads a credit card only and provides selected beverage.- It checks temperature and serves the drink cold or hot.- If balance of a credit card is not enough to buy the beverage, a machine refuse the demand.



SVM Control

Sensor Beverage

Screen

Button

Reader

Beverage

Display

Temperature sensor input

Beverage1 inputBeverage2 input

Card reader input

Event List- Temperature sensor input // reads temperature- Button input // identify button- Card reader input // checks card- Beverage // provides beverage- Display // display machine information

DFD Level 0


SVM Control

0

Temperature Sensor Beverage

Screen

Beverage 1 Button

Card Reader

Beverage

Display


Beverage1 input

Card reader input

Beverage 2 Button

Beverage2 input

Digital Clock

Tick

Data dictionary (생략)

DFD Level 1


Beverage

Display


Beverage1 input

Card reader input

Beverage2 input

Tick

Input Control

1

Beverage Request& Card Data

Beverage & Screen Control

2

Process Specification- Input Control- Beverage & Screen Control

DFD Level 2


Temperature sensorinput

Beverage1 input

Tick

Temperature sensor

interface1.1 Temperature

Beverage Kind

Button 1 interface

1.2

Button 2 interface

1.3

Card Reader interface

1.4

Beverage2 input

Card input

Temperature Degree

1.5

BeverageKind1.5

CardInformation

1.6

Temperature

Card Data

Process Specification- Temperature sensor interface- Button 1 interface- Button 2 interface- Card Reader interface- Temperature Degree- Beverage kind- Card information

DFD Level 2


Beverage Command

Display Command

Main Control

2.1

Temperature

Beverage Kind

Card Data

Beverage Interface

2.2

Display Interface

2.3

Process Specification- Main Control- Beverage Interface- Display Interface

DFD Level 3 (Controller)


Beverage CommandDisplay Command

Enable

Controller2.1.1

Temperature

Beverage Kind

Card Data

Idle2.1.2

Disable Hot/12.1.3

Cold/12.1.4

Hot/22.1.5

Cold/22.1.6





Tick

Trigger

Trigger

Trigger

Trigger

Refuse2.1.7


DFD Level 4 – State Transition Diagram


/Enable “Idle”

Idle

Refuse

Tick [card.balance < 100 ]/Disable “Idle”Trigger “Refuse”

Tick/Enable “Idle”

Hot 1Hot 2 Cold 1

Cold 2


Tick [card.balance > 100 && B1 && C]/Disable “Idle”Trigger “Hot/1”

Tick [card.balance > 100 && B2 && C]/Disable “Idle”Trigger “Hot/2”

Tick [card.balance > 100 && B2 && H]/Disable “Idle”Trigger “Cold/1”

Tick [card.balance > 100 && B2 && H]/Disable “Idle”Trigger “Cold/2”





Practice – Assignment #1

• Complete the RVC analysis in more details.

– Consider the “Dust,” “Stop” …

– You may have several controller

– 9/23 자정: ecampus 과제란 업로드


Practice – Assignment #2

• Performing structured analysis for printer management controller

– 컨트롤러는 요청을 제어하여 프린터에 작업 부여

– 3개의 프린터 (2대 black, 1대 color)

– 프린터는 토너와 용지의 잔량을 감지 (sensor)

– 10/6 자정: ecampus 과제란 업로드


References

• Modern Structured Analysis, Edward Yourdon, 1989.

• Introduction to System Analysis and Design: a Structured Approach, Penny A. Kendall, 1996.

• Zhou Qun, Kendra Hamilton, and Ibrahim Jadalowen (2002). Structured Analysis and Structured Design (SASD) - Class Presentaionhttp://pages.cpsc.ucalgary.ca/~jadalow/seng613/Group/


http://pages.cpsc.ucalgary.ca/~jadalow/seng613/Group/

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