Smart Home Technologies

System Engineering

System Engineering in Intelligent Environments Intelligent Environments are complex

systems consisting of various components Building infrastructure Sensor and actuator hardware Database system Prediction and decision making Interaction with inhabitants

Design and construction of such systems requires a systematic approach Precise specifications are important System has to be treated as a whole

The Goals of System Engineering

Increase the probability of success Assure that the design addresses the actual

problems Ensure that the desired design is technologically

possible Reduce risk

Assess the potential risks Refine design to address risks

Reduce total-life-cycle cost Reduce the likelihood of large-scale redesign

System Engineering System engineering addresses the

complete system as a whole “Put software into context”

Relate software to hardware Address work flow and other human activities Business model

Business Process Engineering Focus on a business enterprise

Product Engineering Focus on a product to be built

System Elements Systems generally consist of a large

number of elements and processes that combine in various ways to address a given problem Software Hardware People Database Documentation Procedures

DefineRequirements

DefineRequirements

InvestigateAlternativesInvestigateAlternatives

Full-ScaleDesign

Full-ScaleDesign

ImplementationImplementationIntegration

& TestIntegration

& Test

Operation, Maintenance& Evaluation

Operation, Maintenance& Evaluation

Retirement,Disposal &

Replacement

Retirement,Disposal &

Replacement

The System Life Cycle

The System Design Process

The vee Life-Cycle Model

MissionAnalysis

SystemRequirements

FunctionalDecomposition

PhysicalDecomposition

Operation &Retirement

FinalSystem Test

VerifySubsystems

TestComponents

BuildComponents

Test Plan

Verification Plan

Validation Plan

Continuous Quality Improvement Plan

The design downstroke and the manufacturing upstroke

System Engineering System engineering is aimed at

managing the system life cycle throughout the specification, design, and construction phases In a business this has to involve

management, engineering, and human factors concerns

Requires understanding of all the components that make up a system

Management Element

Plan andOrganize

Control

Technical Element

AnalyzeProblem

SynthesizeSolutionVerify

Solution

Assess and

Select

Plans and Direction

Outcomes and Decisions

Requirements

Physical Solutions

Systems Engineering Process

Systems Engineering Process

CustomerNeeds

State theProblem

InvestigateAlternatives

Model theSystem Integrate Launch

the System Outputs

Re-evaluate Re-evaluate Re-evaluate Re-evaluate Re-evaluate

AssessPerformance

Re-evaluate

Many steps are involved in systems engineering Requirements engineering System modeling Risk analysis System integration

Steps are not serial but rather parallel and highly iterative

Requirements Engineering Requirements engineering attempts to

specify a system that meets the customer’s needs and expectations. Requirements elicitation Requirements analysis Specification Modeling Validation Management

Requirements Discovery

WriteSystem

Requirements

RewriteRequirements

No

ProblemStatement

Ask Why Each

RequirementIs Needed

RewriteRequirements

DefineFiguresof Merit

Validatethe Set of

RequirementsValid? Yes

CustomerConcurs?

No

ValidatedRequirements

System requirements have to be determined in collaboration with the customer Preferences

Low energy consumption Automatic taping of favorite TV shows

Mandatory requirements Maintain temperature Prevent intrusion

Requirements Elicitation Eliciting requirements from customers is

an important and difficult process that poses many challenges Scope:

Defining the system boundary Lack of clarity on overall objectives

Understanding: Customer not skilled Doesn’t state the obvious Requirements ambiguous, conflicting, …

Volatility: Requirements change over time

Requirements Elicitation

Requirements elicitation process: Assess feasibility Identify people and their roles Define technical environment Identify domain constraints Select elicitation methods Solicit participation from several perspectives Identify ambiguous requirements Create usage scenarios

Requirements Specification

Requirements specifications have to be formalized so that they can be used in the design and construction process Elements of a Specification:

Written documents Graphical models Formal mathematical models

Final work product: System Specification

Requirements Validation To assure that requirements

specifications can be used and will lead to good designs they have to be evaluated

Are requirements stated clearly? Are requirements verified by an identified source? Are requirements consistent with overall objective? Are requirements consistent with domain constraints? Are requirements essential to overall objective? Are requirements bounded and unambiguous? Are requirements conflicting with other requirements? Are requirements sufficiently abstract? Are requirements achievable in the technical

environment? Are requirements testable, with specified tests? Are requirements traceable to the system model?

System Modeling

Once requirements are specified, systems engineering aims at forming a system model at various resolutions At each resolution:

Define processes Represent process behavior List process assumptions Define external and internal inputs Model linkages (control, data, I/O)

System Modeling

System modeling identifies and defines the main aspects and specifications of the system Assumptions

range of allowable data Simplifications

partition data into categories Limitations

bounds on functionality Constraints

guide the implementation Preferences

indicate preferred architecture (data, functions, technology)

System Modeling Part of the role of system modeling is to

translate the requirements specifications into a possible design and to identify potential problems Evaluate the system’s components in

relation to one another Link requirements to system components Validate assumptions about data flow, work

flow, input / output, ...

Risk Management Risk assessment and management

identifies and assesses different risks in the development process and of the product Product risk

Product performance Reliability of home access Consistency of AC system Cost of door authentication system

Project risk Cost, schedule and process performance

Duration of the technology development Cost of production

Safety and environmental risk Risks to the public

Reliability of outdoor robots

Risk Management

Risk management in industrial practice is a tradeoff between costs and risks

“Good risk management will not prevent bad things from happening. But when bad things happen, good risk management will have anticipated them and will reduce their negative effects”

System Engineering in Risk-Prone Environments

At NASA, the probability of mission failure was about 10-2, but the severity was near 1. The product of these numbers was big, so they did lots of systems engineering.

At a big software house, the probability that a new system will destroy user files was about 1, but their perceived severity was around 10-6. They did not care if J.Q. Public lost a few files. Therefore, they did little systems engineering.

Construction And Integration

The construction phase attempts to take the models and specifications and translate them into a product Construction focuses on the details

Implementation of individual elements

Goals: Implement the architectures and infrastructure Integrate and deploy the completed system

Requirements Management Assurance of conformity of models and

constructed products with the requirements is an important part of system engineering Active throughout the life-cycle Identify, control, and track:

New requirements Changes to requirements

Tools: Traceability Table

Relates requirements to features, source, dependency, subsystem, interface, etc.

System Engineering TasksState the problem Design the system Produce

documentation Understand customer needs

Sensitivity analyses

Lead teams

Discover requirements

Assess & manage risk

Assess performance

Validate requirements

Reliability analyses

Prescribe tests

Investigate alternatives

Integrate system components

Conduct reviews

Define quantitative measures

Design & manage interfaces

Verify requirements

Model the system Execute configuration management

Perform total system test

Functional decomposition

Project management

Re-evaluate & Improve quality

Conclusions System engineering is important for the

successful construction of large scale systems Assure requirements are specified correctly

Engineers and scientists do not necessarily know what inhabitants of intelligent environments really need

Model the system to assess feasibility Often intended features are not feasible or too costly

The self-regulating home is not (yet) technologically possible Assess economic viability

To make intelligent environments reality they have to be economical and fit the requirements of users

Assess project risks and track requirements Economic as well as physical risks to inhabitants have to

be taken into account to field a system A good engineer in intelligent environments

has to have some understanding of all aspects of system engineering