Radio Antenna

High Gain Radio Dish Antenna

Photovoltaic Solar Power Panels

Payload unit (scientific instruments)

Platform unit: batteries, computer,attitude control, communications

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Do Worthwhile Space Science

Launch into Space

New Instrument Designs

Long Lifetime

Reliability Goal

Low Mass

Key Goal

Very Reliable

Key Goal

Keep on Station a Long Time

Low Power Consumption

Cautious Design

Large Supply of Thruster Fuel

Many Different Instruments

Long Time for Science

Spares for Vital Functions

High Cost per Kilogram

Commercial Obstacle

Affordable Price

Commercial GoalEquipment Failure

Reliability Obstacle

Radiation Damage

Functional Obstacle

Initial (Top-Level) Goal

The cutting machine is acceptably safe

Argument that all safety requirements are met

Guard frame prevents injury to operator

Earth leakage trip prevents electric shock

Electrical safety test

results

Argument that all identified hazards

are excludedKnown

Hazards

… …

PassengerTram

Company

Be carriedfrom A to B

Earn incomefrom fares

D

D

D

D

D

D

D D

Quickly

Safely

i* Strategic Dependency

Passenger

Be carriedfrom A to B

Earn incomefrom fares

D D

D D

OperateRoute

OperateTimetable

MaintainVehicles

MaintainStaff

DriveVehicles

Pick Up/Set Down

RecruitStaff

TrainStaff

PayStaff

CollectFares

i* Strategic Rationale

D

DQuickly

PublishTimetable

Cook

Owner / Manager

Customer / Diner

Supplier

TaxmanPublic Health Dept

correct tax paid

good pay

value for money

good food

safety

hygiene rules obeyed

profit

efficient staff

no hassle

top chef

paid on time, in full

career success

reputationno staff absences

free to cook distinctive menus

good equipment

best ingredientswell-trained staff

adequate budget

no hygiene problems

low running costs

enjoyable ambience

good service

Cook

Owner / Manager

Customer / Diner

Public Health Dept

safety

hygiene rules obeyed

well-trained staff

no hygiene problems

low running costs

Creating a Goal Model in a Customised Tool

A Threat is an Obstacle involving hostile intent

Goals can be for product qualities as well as for

functions

Representing a Goal Model in a Requirements Database

Attributes used to characterise goals

Database traceability links used to record goal

relationships and their directions