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Chapter 6System Engineering

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System Engineering What is a computer-based system?

A set or arrangement of elements that are organized to accomplish some predefined goal by processing information

Elements of a computer-based system Software Hardware People Database Documentation Procedures

Systems A hierarchy of macro-elements

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The Hierarchy

World view

Business orProduct Domain

Domain of interest

Domain view

System element

Element view

Detailed view

e.g., School Administrative Information System

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System Modeling

Define the processes that serve the needs of the view under consideration.

Represent the behavior of the processes and the assumptions on which the behavior is based.

Explicitly define both exogenous and endogenous input to the model. exogenous inputs link one constituent of a given view with

other constituents at the same level of other levels; endogenous input links individual components of a

constituent at a particular view. Represent all linkages (including output) that will enable

the engineer to better understand the view.

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Business Process Engineering (BPE)

Uses an integrated set of procedures, methods, Uses an integrated set of procedures, methods, and tools to identify how information systems and tools to identify how information systems can best meet the strategic goals of an can best meet the strategic goals of an enterpriseenterprise

Focuses first on the enterprise and then on the Focuses first on the enterprise and then on the business areabusiness area

Creates enterprise models, data models and Creates enterprise models, data models and process modelsprocess models

Creates a framework for better information Creates a framework for better information management distribution, and controlmanagement distribution, and control

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System Architectures

Three different architectures must be analyzed and designed within the context of business objectives and goals: data architecture applications architecture technology infrastructure

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System Architectures (cont.)

Data architecture provides a framework for the information needs of a

business or business function i.e., database schema

Application architecture encompasses those elements of a system that transform

objects within the data architecture for some business purpose

i.e., programs Technology infrastructure

provides the foundation for the data and application architectures

i.e., hardware, software,

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The BPE Hierarchy Information strategy planning (ISP)

strategic goals defined success factors/business rules identified enterprise model created

Business area analysis (BAA) processes/services modeled interrelationships of processes and data

Application Engineering a.k.a ... software engineering modeling applications/procedures that address (BAA)

and constraints of ISP Construction and delivery

using CASE and 4GTs, testing

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The BPE Hierarchy (cont.)

Information strategy planning(World view)

The enterprise

Business area

Business area analysis(Domain view)

Processing requirement

Business systemdesign

(Element view)

Construction&

Integration(Detailed view)

A business area

Informationsystem

SoftwareEngineering

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Information Strategy Planning

Management issues define strategic business goals/objectives isolate critical success factors conduct analysis of technology impact perform analysis of strategic systems

Technical issues create a top-level data model cluster by business/organizational area refine model and clustering

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Defining Objectives and Goals

Objective—general statement of direction Goal—defines measurable objective:

“reduce manufactured cost of our product” Subgoals:

decrease reject rate by 20% in first 6 months gain 10% price concessions from suppliers re-engineer 30% of components for ease of

manufacture during first year Objectives tend to be strategic while

goals tend to be tactical

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Business Area Analysis Define “naturally cohesive groupings of

business functions and data” (Martin) Perform many of the same activities as ISP,

but narrow scope to individual business area Identify existing (old) information systems /

determine compatibility with new ISP model define systems that are problematic defining systems that are incompatible with new

information model begin to establish re-engineering priorities

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The BAA Process

salesacct

manufacturing

QC

eng’ring

distribution

admin.

DataModel

ProcessDecomposition

DiagramMatrices

e.g.,entity/process

matrix

Process Flow

Models

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Product Engineering

Goal: To translate customer’s desire into a working product

Consist of four system components Software Hardware Data People

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Product Engineering (cont.)

System analysis(World view)

The completeproduct

capabilities

Componentengineering

(Domain view)

Processing requirement

Analysis & DesignModeling

(Element view)

Construction&

Integration(Detailed view)

software

function

SoftwareEngineering

programcomponent

hardware

data behavior

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Product Architecture Template

user interface processing

inputprocessing

outputprocessing

maintenance and self-test

process and controlfunctions

Proposed by Hatley and Pirbhai, also known as Hatley-Pirbhai modeling

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Architecture Flow Diagram (AFD)

bar codereader

subsystem

bar codedecoding

subsystem

data baseaccess

subsystem

shuntcontrol

subsystem

reportformating

subsystem

diagnosticssubsystem

operatorinterface

subsystem

shuntcontroller

mainframecommunications

driver

operator requests CLSS queries, reports, displays

shunt control statusbar code acquisition request

bar code

pulse tach input

linespeed

bar codereader status

sensor status

raw barcode data

partnumber

reportrequests

binlocation

key

sort records

formatedreporting data

sorting reports

shunt commands

CLSS reports

BCR statusshunt status

communications status

timing/location data

operatorinterface

data acquisitioninterface diagnostic interface output interface

CLSS processing & control

sensor dataacquisitionsubsystem

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SFD Hierarchy

A B

C

Top level AFD

AFD for B

AFD for A

AFD for C

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System Modeling with UML Deployment diagrams (Modeling hardware)

Each 3-D box depicts a hardware element that is part of the physical architecture of the system

Activity diagrams (Modeling software) Represent procedural aspects of a system element

Class diagrams (Modeling data) Represent system level elements in terms of the data that

describe the element and the operations that manipulate the data

Use-case diagrams (Modeling people) Illustrate the manner in which an actor interacts with the

system*These and other UML models will be discussed later

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Deployment Diagram

CLSS processor

Sorting subsystem

Sensor dataacquisition subsystem

Operator display

shunt controller

Conveyor Pulse tach

Bar code reader Shunt actuator

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Activity Diagram

get conveyor speed

send shunt

control data

get shunt status read bar code

start conveyor line

determine bin location

valid bar code

set for reject bin

conveyor in motion

read bar code

get conveyor status

produce report entry

conveyor stopped

invalid bar code

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Class Diagram

Box

barcode forwardSpeed conveyorLocation height width depth weight contents

readBarcode() updateSpeed() readSpeed() updateLocation() readLocation() getDimensions() getWeight() checkContents()

class name

attributes note use of capital letter for multi-word attribute names

operations (parentheses at endof name indicate the list of attributes that theoperation requires)

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Use-Case Diagram

Request bar code

Request shunt control status

Request box processing report

Update product database

Run system diagnostics

CLSS operator