handout 6

* Property of STI of 21

Requirements Analysis

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Requirement Analysis

Configuration Management

Types of Requirement

Structure Charts

State Transition Diagram

Elements of Analysis Models

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* Property of STIPage 3 of 21


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Analysis and a bridge between system engineering and software design

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software engineering task that bridges the gap between system-level software allocation and software design.

enables the system engineer to specify software function and performance, indicate software’s interface with other system elements, and establish constraints that software must meet.

allows the software engineer to refine the software allocation and build models of the data, functional, and behavioral domains that will be treated by software.

provides the software designer with models that can be translated into data, architectural, interface, and procedural design.

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Five (5) Areas of Effort

Problem recognition

Evaluation and synthesis

Modeling

Specification

Review

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REQUIREMENTS

SYSTEM DESIGNERCUSTOMER

DEFINITION SPECIFICATION

CONFIGURATIONMANAGEMENT

What the customercan expect thesystem to do

Technical descriptionof system

characteristics


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REQUIREMENTS

INTERFACES

DATA

PhysicalEnvironment

QualityAssurance

Security

Resources

Users andHuman Factors

Functionality

Documentation

Types of Requirements

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A set of procedures that track the requirements that define a system the design modules that are generated from

the requirements the program code that implements the design the tests that verify the functionality of the

system the documents that describe the system

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Structure Charts

shows how an information system is organized in a hierarchy of components, called modules

its purpose is to show graphically how the parts of a system or program are related to each other, in terms of passing data and in terms of the basic components of structured programming: sequence, selection, and repetition

redefines the flow and processing of data from data flow diagrams into a structure of system components that follow certain principles of good program design

used to show the breakdown of a system into programs and the internal structure of programs written in third- and fourth-generation languages

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Structure Charts

System or"boss"

GetB

MakeC

PutC

GetA

MakeB

An illustration of the hierarchy of a structure chart

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readinguserinput

monitoringsystemstatus

acting on asensor event

displayinguser

feedback

start/stop switchinvoke monitor &control system

sensor eventinvoke monitor &control system

sensor eventinvoke display

messages & status

sensor eventinvoke monitor & control system

display actions statusinvoke interact with userblink flag

invoke displaymessages & status

sensor eventinvoke display

messages & status

time outinvoke interact

with user

State-transition diagram for Safe Home

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indicates how the system behaves as a consequence of external events

represents the behavior of a system by depicting its states and the events that cause the system to change state

indicates what actions (e.g., process activation) are taken as a consequence of a particular event

serves as the basis for behavioral modeling

State any observable mode of behavior

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Objectives to describe what the customer requires

to establish a basis for the creation of a software design

to define a set of requirements that can be validated once the software is built

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Entity-Relationship

Diagram

State-TransitionDiagram

Data FlowDiagram

Data Dictionary

Dat

a

Obj

ect

Des

criptio

n

Control

Specification

(CSPEC)

Process

Specification

(PSP

EC)

The structure of the analysis model

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Data Objects, Attributes, and Relationships

Data Objects representation of almost any composite

information that must be understood by software

Attributes define the properties of a data object and

take on one of three different characteristics:

name an instance of the data object describe the instance make reference to another instance in

another table

Relationships data objects are connected to one another

in a variety of different ways

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Data Dictionary repository containing descriptions of all

data objects consumed or produced by the software

Entity-Relationship Diagram (ERD) depicts relationships between data objects

Data Flow Diagram (DFD) provides an indication of how data are

transformed as they move through the system and depicts the functions (and subfunctions) that transform the data flow

State-Transition Diagram (STD) indicates how the system behaves as a

consequence of external events

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Data Objects, Attributes, and Relationships

Objects: Relationships:Attributes:

NameAddressAgeDriver's licenseNumber

MakeModelID numberBody typeColor

owns

Example of data objects, attributes, and relationships

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Cardinality and Modality

Cardinality the specification of the number of

occurrences of one [object] that can be related to the number of occurrences of another [object]

can be classified as one-to-one (1:1), one-to-many (1:N), and many-to-many (M:N)

Modality the modality is zero if there is no explicit

need for the relationship to occur or the relationship is optional

the modality is 1 if an occurrence of the relationship is mandatory

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Entity Relationship Diagram

detailed, logical representation of the entities, associations, and data elements for an organization or business area

dealership

manufacturer car

shipper

stockslicenses

builds

contracts transports

An expanded ERD

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Repair actionCustomer

Cardinality:Implies that a single

customer awaits repair action(s)

Cardinality:Implies that there may be

many repair action(s)

Modality: MandatoryImplies that in order to havea repair action(s), we must

have a customer

Modality: OptionalImplies that there may be asituation in which a repair

action is not necessary

is provided with


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computer-basedsystem

externalentity

externalentity

externalentity

externalentity

externalentity

inputinformation

inputinformation

outputinformation

outputinformation

outputinformation

Data Flow Diagram

• graphical technique that depicts information flow and the transforms that are applied as data move from input to output

• also known as a data flow graph or a bubble chart

Information flow model

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Data Dictionary

has been proposed as a quasi-formal grammar for describing the content of objects defined during structured analysis

organized listing of all data elements that are pertinent to the system, with precise, rigorous definitions so that both user and system analyst will have a common understanding of inputs, outputs, components of stores and intermediate calculations

contains the following information:namealiaswhere-used/how-usedcontent descriptionsupplementary information

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handout 6

Design