Socio-technical Socio-technical SystemsSystems

Hewijin Christine Jiau Hewijin Christine Jiau 焦惠津焦惠津

September 2007September 2007

ObjectivesObjectives To explain what a socio-technical system is and the To explain what a socio-technical system is and the

distinction between this and a computer-based systemdistinction between this and a computer-based system To introduce the concept of emergent system To introduce the concept of emergent system

properties such as reliability and securityproperties such as reliability and security To explain system engineering and system To explain system engineering and system

procurement processesprocurement processes To explain why the organisational context of a system To explain why the organisational context of a system

affects its design and useaffects its design and use To discuss legacy systems and why these are critical to To discuss legacy systems and why these are critical to

many businessesmany businesses

Topics coveredTopics covered Emergent system propertiesEmergent system properties Systems engineeringSystems engineering Organizations, people and computer systems Organizations, people and computer systems Legacy systemsLegacy systems

What is a system?What is a system? A purposeful collection of inter-related A purposeful collection of inter-related

components working together to achieve some components working together to achieve some common objective. common objective.

A system may include software, mechanical, A system may include software, mechanical, electrical and electronic hardware and be operated electrical and electronic hardware and be operated by people.by people.

System components are dependent on other System components are dependent on other system componentssystem components

The properties and behaviour of system The properties and behaviour of system components are inextricably inter-mingledcomponents are inextricably inter-mingled

System categoriesSystem categories Technical computer-based systemsTechnical computer-based systems

Systems that include hardware and software but Systems that include hardware and software but where the operators and operational processes are where the operators and operational processes are not normally considered to be part of the system. not normally considered to be part of the system. The system is not self-aware.The system is not self-aware.

Socio-technical systemsSocio-technical systems Systems that include technical systems but also Systems that include technical systems but also

operational processes and people who use and operational processes and people who use and interact with the technical system. Socio-technical interact with the technical system. Socio-technical systems are governed by organisational policies systems are governed by organisational policies and rules.and rules.

Socio-technical system Socio-technical system characteristicscharacteristics

Emergent propertiesEmergent properties Properties of the system of a whole that depend on the Properties of the system of a whole that depend on the

system components and their relationships.system components and their relationships. Non-deterministicNon-deterministic

They do not always produce the same output when They do not always produce the same output when presented with the same input because the systems’s presented with the same input because the systems’s behaviour is partially dependent on human operators.behaviour is partially dependent on human operators.

Complex relationships with organisational objectivesComplex relationships with organisational objectives The extent to which the system supports organisational The extent to which the system supports organisational

objectives does not just depend on the system itself.objectives does not just depend on the system itself.

Emergent propertiesEmergent properties Properties of the system as a whole rather than Properties of the system as a whole rather than

properties that can be derived from the properties that can be derived from the properties of components of a systemproperties of components of a system

Emergent properties are a consequence of the Emergent properties are a consequence of the relationships between system componentsrelationships between system components

They can therefore only be assessed and They can therefore only be assessed and measured once the components have been measured once the components have been integrated into a systemintegrated into a system

Examples of emergent propertiesExamples of emergent properties

Property D e s c r i p t i o n

V o l u m e T h e v o l u m e o f a s y s t e m ( t h e t o t a l s p a c e o c c u p i e d ) v a r i e s d e p e n d i n g o n h o w t h ec o m p o n e n t a s s e m b l i e s a r e a r r a n g e d a n d c o n n e c t e d .

R e l i a b i l i t y S y s t e m r e l i a b i l i t y d e p e n d s o n c o m p o n e n t r e l i a b i l i t y b u t u n e x p e c t e d i n t e r a c t i o n s c a nc a u s e n e w t y p e s o f f a i l u r e a n d t h e r e f o r e a f f e c t t h e r e l i a b i l i t y o f t h e s y s t e m .

S e c u r i t y T h e s e c u r i t y o f t h e s y s t e m ( i t s a b i l i t y t o r e s i s t a t t a c k ) i s a c o m p l e x p r o p e r t y t h a tc a n n o t b e e a s i l y m e a s u r e d . A t t a c k s m a y b e d e v i s e d t h a t w e r e n o t a n t i c i p a t e d b y t h es y s t e m d e s i g n e r s a n d s o m a y d e f e a t b u i l t - i n s a f e g u a r d s .

R e p a i r a b i l i t y T h i s p r o p e r t y r e f l e c t s h o w e a s y i t i s t o f i x a p r o b l e m w i t h t h e s y s t e m o n c e i t h a s b e e nd i s c o v e r e d . I t d e p e n d s o n b e i n g a b l e t o d i a g n o s e t h e p r o b l e m , a c c e s s t h e c o m p o n e n t st h a t a r e f a u l t y a n d m o d i f y o r r e p l a c e t h e s e c o m p o n e n t s .

U s a b i l i t y T h i s p r o p e r t y r e f l e c t s h o w e a s y i t i s t o u s e t h e s y s t e m . I t d e p e n d s o n t h e t e c h n i c a ls y s t e m c o m p o n e n t s , i t s o p e r a t o r s a n d i t s o p e r a t i n g e n v i r o n m e n t .

Types of emergent propertyTypes of emergent property Functional properties Functional properties

These appear when all the parts of a system work together These appear when all the parts of a system work together to achieve some objective. For example, a bicycle has the to achieve some objective. For example, a bicycle has the functional property of being a transportation device once functional property of being a transportation device once it has been assembled from its components.it has been assembled from its components.

Non-functional emergent propertiesNon-functional emergent properties Examples are reliability, performance, safety, and security. Examples are reliability, performance, safety, and security.

These relate to the behaviour of the system in its These relate to the behaviour of the system in its operational environment. They are often critical for operational environment. They are often critical for computer-based systems as failure to achieve some computer-based systems as failure to achieve some minimal defined level in these properties may make the minimal defined level in these properties may make the system unusable.system unusable.

Because of component inter-dependencies, Because of component inter-dependencies, faults can be propagated through the system.faults can be propagated through the system.

System failures often occur because of System failures often occur because of unforeseen inter-relationships between unforeseen inter-relationships between components.components.

It is probably impossible to anticipate all It is probably impossible to anticipate all possible component relationships.possible component relationships.

Software reliability measures may give a false Software reliability measures may give a false picture of the system reliability.picture of the system reliability.

System reliability engineeringSystem reliability engineering

Hardware reliability Hardware reliability What is the probability of a hardware component failing What is the probability of a hardware component failing

and how long does it take to repair that component?and how long does it take to repair that component?

Software reliabilitySoftware reliability How likely is it that a software component will produce an How likely is it that a software component will produce an

incorrect output. Software failure is usually distinct from incorrect output. Software failure is usually distinct from hardware failure in that software does not wear out. hardware failure in that software does not wear out.

Operator reliability Operator reliability How likely is it that the operator of a system will make an How likely is it that the operator of a system will make an

error?error?

Influences on reliabilityInfluences on reliability

Reliability relationshipsReliability relationships Hardware failure can generate spurious signals Hardware failure can generate spurious signals

that are outside the range of inputs expected by that are outside the range of inputs expected by the software.the software.

Software errors can cause alarms to be activated Software errors can cause alarms to be activated which cause operator stress and lead to which cause operator stress and lead to operator errors.operator errors.

The environment in which a system is installed The environment in which a system is installed can affect its reliability.can affect its reliability.

The ‘shall-not’ propertiesThe ‘shall-not’ properties Properties such as performance and reliability Properties such as performance and reliability

can be measured.can be measured. However, some properties are properties that However, some properties are properties that

the system should not exhibitthe system should not exhibit Safety - the system should not behave in an unsafe Safety - the system should not behave in an unsafe

way;way; Security - the system should not permit Security - the system should not permit

unauthorised use.unauthorised use. Measuring or assessing these properties is very Measuring or assessing these properties is very

hard.hard.

Systems engineeringSystems engineering Specifying, designing, implementing, validating, Specifying, designing, implementing, validating,

deploying and maintaining socio-technical deploying and maintaining socio-technical systems.systems.

Concerned with the services provided by the Concerned with the services provided by the system, constraints on its construction and system, constraints on its construction and operation and the ways in which it is used.operation and the ways in which it is used.

The system engineering processThe system engineering process Usually follows a ‘waterfall’ model because of the need Usually follows a ‘waterfall’ model because of the need

for parallel development of different parts of the for parallel development of different parts of the systemsystem Little scope for iteration between phases because hardware Little scope for iteration between phases because hardware

changes are very expensive. Software may have to changes are very expensive. Software may have to compensate for hardware problems.compensate for hardware problems.

Inevitably involves engineers from different disciplines Inevitably involves engineers from different disciplines who must work togetherwho must work together Much scope for misunderstanding here. Different Much scope for misunderstanding here. Different

disciplines use a different vocabulary and much disciplines use a different vocabulary and much negotiation is required. Engineers may have personal negotiation is required. Engineers may have personal agendas to fulfil.agendas to fulfil.

The systems engineering processThe systems engineering process

S y s t e mi n t e g r a t i o n

S u b - s y s t e md e v e l o p m e n t

S y s t e m

d e s i g n

R e q u i r e m e n t sd e f i n i t i o n

S y s t e mi n s t a l l a t i o n

S y s t e m

e v o l u t i o n

S y s t e md e c o m m i s s i o n i n g

Inter-disciplinary involvementInter-disciplinary involvement

A T C s y s t e m s

e n g i n e e r i n g

E l e c t ro n i c

e n g i n e e r i n g

E l e c t r i c a l

e n g i n e e r i n g

U s e r i n t e r f a c e

d e s i g n

M e c h a n i c a l

e n g i n e e r i n g

A r c h i t e c t u r e

S t r u c t u r a l

e n g i n e e r i n g

S o f t w a r e

e n g i n e e r i n g

C i v i l

e n g i n e e r i n g

System requirements definitionSystem requirements definition Three types of requirement defined at this stageThree types of requirement defined at this stage

Abstract functional requirements. System Abstract functional requirements. System functions are defined in an abstract way;functions are defined in an abstract way;

System properties. Non-functional requirements System properties. Non-functional requirements for the system in general are defined;for the system in general are defined;

Undesirable characteristics. Unacceptable system Undesirable characteristics. Unacceptable system behaviour is specified.behaviour is specified.

Should also define overall organisational Should also define overall organisational objectives for the system.objectives for the system.

System objectivesSystem objectives Should define why a system is being procured Should define why a system is being procured

for a particular environment.for a particular environment. Functional objectivesFunctional objectives

To provide a fire and intruder alarm system for To provide a fire and intruder alarm system for the building which will provide internal and the building which will provide internal and external warning of fire or unauthorized intrusion.external warning of fire or unauthorized intrusion.

Organisational objectivesOrganisational objectives To ensure that the normal functioning of work To ensure that the normal functioning of work

carried out in the building is not seriously carried out in the building is not seriously disrupted by events such as fire and unauthorized disrupted by events such as fire and unauthorized intrusion.intrusion.

System requirements problemsSystem requirements problems Complex systems are usually developed to Complex systems are usually developed to

address wicked problemsaddress wicked problems Problems that are not fully understood;Problems that are not fully understood; Changing as the system is being specified.Changing as the system is being specified.

Must anticipate hardware/communications Must anticipate hardware/communications developments over the lifetime of the system.developments over the lifetime of the system.

Hard to define non-functional requirements Hard to define non-functional requirements (particularly) without knowing the (particularly) without knowing the component structure of the system.component structure of the system.

The system design processThe system design process Partition requirementsPartition requirements

Organise requirements into related groups. Organise requirements into related groups. Identify sub-systemsIdentify sub-systems

Identify a set of sub-systems which collectively can meet Identify a set of sub-systems which collectively can meet the system requirements.the system requirements.

Assign requirements to sub-systemsAssign requirements to sub-systems Causes particular problems when COTS are integrated.Causes particular problems when COTS are integrated.

Specify sub-system functionality.Specify sub-system functionality. Define sub-system interfacesDefine sub-system interfaces

Critical activity for parallel sub-system development.Critical activity for parallel sub-system development.

The system design processThe system design process

P a r t i t i o nr e q u i r e m e n t s

I d e n t i f ys u b - s y s t e m s

A s s i g n r e q u i r e m e n t st o s u b - s y s t e m s

S p e c i f y s u b - s y s t e mf u n c t i o n a l i t y

D e f i n e s u b - s y s t e mi n t e r f a c e s

System design problemsSystem design problems Requirements partitioning to hardware, Requirements partitioning to hardware,

software and human components may involve a software and human components may involve a lot of negotiation. lot of negotiation.

Difficult design problems are often assumed to Difficult design problems are often assumed to be readily solved using software.be readily solved using software.

Hardware platforms may be inappropriate for Hardware platforms may be inappropriate for software requirements so software must software requirements so software must compensate for this.compensate for this.

Requirements and designRequirements and design Requirements engineering and system design Requirements engineering and system design

are inextricably linked.are inextricably linked. Constraints posed by the system’s environment Constraints posed by the system’s environment

and other systems limit design choices so the and other systems limit design choices so the actual design to be used may be a requirement.actual design to be used may be a requirement.

Initial design may be necessary to structure the Initial design may be necessary to structure the requirements.requirements.

As you do design, you learn more about the As you do design, you learn more about the requirements.requirements.

Spiral model of Spiral model of requirements/designrequirements/design

System Requirements and Design

P roblemD efinition

R eview andA ssessm ent

R equirem entsE lic itation and

A naly sis

A rchitecturalD esign

Start

System modellingSystem modelling An architectural model presents an abstract An architectural model presents an abstract

view of the sub-systems making up a systemview of the sub-systems making up a system May include major information flows between May include major information flows between

sub-systemssub-systems Usually presented as a block diagramUsually presented as a block diagram May identify different types of functional May identify different types of functional

component in the modelcomponent in the model

Burglar alarm systemBurglar alarm system

A l a r mc o n t r o l l e r

V o i c es y n t h e s i s e r

M o v e m e n ts e n s o r s

S i r e n

D o o rs e n s o r s

T e l e p h o n ec a l l e r

E x t e r n a lc o n t r o l c e n t r e

Sub-system descriptionSub-system description

Sub-system Description

Movement sensors Detects movement in the rooms monitored by the system

Door sensors Detects door opening in the external doors of the building

Alarm controller Controls the operation of the system

Siren Emits an audible warning when an intruder is suspected

Voice synthesizer Synthesizes a voice message giving the location of the suspected intruder

Telephone caller Makes external calls to notify security, the police, etc.

ATC system architectureATC system architectureD a t a c o m m s.

s y s t e mT r a n s p o n d e r

s y s t e mR a d a r

s y s t e mA i r c r a f tc o m m s.

T e l e p h o n es y s t e m

F l i g h t p l a nd a t a b a s e

B a c k u pp o s i t i o n

p r o c e s s o r

P o s i t i o n

p r o c e s s o r

C o m m s .

p r o c e s s o r

B a c k u p c o m m s.

p r o c e s s o r

A i r c r a f t

s i m u l a t i o ns y s t e m

W e a t h e r m a p

s y s t e m

A c c o u n t i n gs y s t e m

C o n t r o l l e ri n f o . s y s t e m

C o n t r o l l e rc o n s o l e s

A c t i v i t y l o g g i n gs y s t e m

Sub-system developmentSub-system development Typically parallel projects developing the Typically parallel projects developing the

hardware, software and communications.hardware, software and communications. May involve some COTS (Commercial Off-the-Shelf) May involve some COTS (Commercial Off-the-Shelf)

systems procurement.systems procurement. Lack of communication across implementation Lack of communication across implementation

teams.teams. Bureaucratic and slow mechanism for Bureaucratic and slow mechanism for

proposing system changes means that the proposing system changes means that the development schedule may be extended because of the development schedule may be extended because of the need for rework.need for rework.

The process of putting hardware, software and The process of putting hardware, software and people together to make a system.people together to make a system.

Should be tackled incrementally so that sub-Should be tackled incrementally so that sub-systems are integrated one at a time.systems are integrated one at a time.

Interface problems between sub-systems are Interface problems between sub-systems are usually found at this stage.usually found at this stage.

May be problems with uncoordinated deliveries May be problems with uncoordinated deliveries

of system components.of system components.

System integrationSystem integration

After completion, the system has to be installed After completion, the system has to be installed in the customer’s environmentin the customer’s environment Environmental assumptions may be incorrect;Environmental assumptions may be incorrect; May be human resistance to the introduction of May be human resistance to the introduction of

a new system;a new system; System may have to coexist with alternative System may have to coexist with alternative

systems for some time;systems for some time; May be physical installation problems (e.g. May be physical installation problems (e.g.

cabling problems);cabling problems); Operator training has to be identified.Operator training has to be identified.

System installationSystem installation

System evolutionSystem evolution Large systems have a long lifetime. They must evolve Large systems have a long lifetime. They must evolve

to meet changing requirements.to meet changing requirements. Evolution is inherently costlyEvolution is inherently costly

Changes must be analysed from a technical and business Changes must be analysed from a technical and business perspective;perspective;

Sub-systems interact so unanticipated problems can arise;Sub-systems interact so unanticipated problems can arise; There is rarely a rationale for original design decisions;There is rarely a rationale for original design decisions; System structure is corrupted as changes are made to it.System structure is corrupted as changes are made to it.

Existing systems which must be maintained are Existing systems which must be maintained are sometimes called sometimes called legacy systems.legacy systems.

System decommissioningSystem decommissioning Taking the system out of service after its useful Taking the system out of service after its useful

lifetime.lifetime. May require removal of materials (e.g. May require removal of materials (e.g.

dangerous chemicals) which pollute the dangerous chemicals) which pollute the environmentenvironment Should be planned for in the system design by Should be planned for in the system design by

encapsulation.encapsulation. May require data to be restructured and May require data to be restructured and

converted to be used in some other system.converted to be used in some other system.

Organisations/people/systemsOrganisations/people/systems Socio-technical systems are organisational Socio-technical systems are organisational

systems intended to help deliver some systems intended to help deliver some organisational or business goal.organisational or business goal.

If you do not understand the organisational If you do not understand the organisational environment where a system is used, the system environment where a system is used, the system is less likely to meet the real needs of the is less likely to meet the real needs of the business and its users.business and its users.

Human and organisational Human and organisational factorsfactors

Process changesProcess changes Does the system require changes to the work Does the system require changes to the work

processes in the environment? processes in the environment? Job changesJob changes

Does the system de-skill the users in an Does the system de-skill the users in an environment or cause them to change the way environment or cause them to change the way they work? they work?

Organisational changesOrganisational changes Does the system change the political power Does the system change the political power

structure in an organisation? structure in an organisation?

Organisational processesOrganisational processes The processes of systems engineering overlap and The processes of systems engineering overlap and

interact with organisational procurement processes.interact with organisational procurement processes. Operational processes are the processes involved in Operational processes are the processes involved in

using the system for its intended purpose. For new using the system for its intended purpose. For new systems, these have to be defined as part of the system systems, these have to be defined as part of the system design.design.

Operational processes should be designed to be Operational processes should be designed to be flexible and should not force operations to be done in flexible and should not force operations to be done in a particular way. It is important that human operators a particular way. It is important that human operators can use their initiative if problems arise.can use their initiative if problems arise.

Procurement/development Procurement/development processesprocesses

P rocurem entprocess

O perationalprocess

D evelopm entprocess

System procurementSystem procurement Acquiring a system for an organization to meet some Acquiring a system for an organization to meet some

needneed Some system specification and architectural design is Some system specification and architectural design is

usually necessary before procurementusually necessary before procurement You need a specification to let a contract for system You need a specification to let a contract for system

developmentdevelopment The specification may allow you to buy a commercial off-The specification may allow you to buy a commercial off-

the-shelf (COTS) system. Almost always cheaper than the-shelf (COTS) system. Almost always cheaper than developing a system from scratchdeveloping a system from scratch

Large complex systems usually consist of a mix of off Large complex systems usually consist of a mix of off the shelf and specially designed components. The the shelf and specially designed components. The procurement processes for these different types of procurement processes for these different types of component are usually different.component are usually different.

The system procurement processThe system procurement process

C h o o s es u p p l i e r

I s s u e r e q u e s tf o r b i d s

C h o o s es y s t e m

A d a p tr e q u i r e m e n t s

S u r v e y m a rk e t f o re x i s t i n g s y s t e m s

L e t c o n t r a c t f o rd e v e l o p m e n t

N e g o t i a t ec o n t r a c t

S e l e c tt e n d e r

I s s u e r e q u e s tt o t e n d e r

O f f - t h e - s h e l fs y s t e m av a i l a b l e

C u s t o m s y s t e mr e q u i r e d

Procurement issuesProcurement issues Requirements may have to be modified to Requirements may have to be modified to

match the capabilities of off-the-shelf match the capabilities of off-the-shelf components.components.

The requirements specification may be part of The requirements specification may be part of the contract for the development of the system.the contract for the development of the system.

There is usually a contract negotiation period to There is usually a contract negotiation period to agree changes after the contractor to build a agree changes after the contractor to build a system has been selected.system has been selected.

Contractors and sub-contractorsContractors and sub-contractors The procurement of large hardware/software The procurement of large hardware/software

systems is usually based around some principal systems is usually based around some principal contractor.contractor.

Sub-contracts are issued to other suppliers to Sub-contracts are issued to other suppliers to supply parts of the system.supply parts of the system.

Customer liases with the principal contractor Customer liases with the principal contractor and does not deal directly with sub-contractors.and does not deal directly with sub-contractors.

Contractor/Sub-contractor modelContractor/Sub-contractor model

Subcontr actor 2Subcontr actor 1 Subcontr actor 3

P rincipalcontr actor

Sy stemcustom er

Legacy systemsLegacy systems Socio-technical systems that have been developed Socio-technical systems that have been developed

using old or obsolete technology.using old or obsolete technology. Crucial to the operation of a business and it is often Crucial to the operation of a business and it is often

too risky to discard these systemstoo risky to discard these systems Bank customer accounting system;Bank customer accounting system; Aircraft maintenance system.Aircraft maintenance system.

Legacy systems constrain new business processes and Legacy systems constrain new business processes and consume a high proportion of company budgets.consume a high proportion of company budgets.

S y s t e mh a r d w a r e

B u s i n e s sp r o c e s s e s

A p p l i c a t i o ns o f t w a r e

B u s i n e s s p o l i c i e sa n d r u l e s

S u p p o r t s o f t w a r e

A p p l i c a t i o n d a t a

C o n s t r a i n sU s e sU s e sR u n s - o nR u n s - o n

E m b e d sk n o w l e d g e o f

U s e s

Legacy system componentsLegacy system components Hardware - may be obsolete mainframe hardware.Hardware - may be obsolete mainframe hardware. Support software - may rely on support software from Support software - may rely on support software from

suppliers who are no longer in business.suppliers who are no longer in business. Application software - may be written in obsolete Application software - may be written in obsolete

programming languages.programming languages. Application data - often incomplete and inconsistent.Application data - often incomplete and inconsistent. Business processes - may be constrained by software Business processes - may be constrained by software

structure and functionality.structure and functionality. Business policies and rules - may be implicit and Business policies and rules - may be implicit and

embedded in the system software.embedded in the system software.

S o c i o - t e c h n i c a l s y s t e m

H a r d w a r e

S u p p o r t s o f t w a r e

A p p l i c a t i o n s o f t w a r e

B u s i n e s s p r o c e s s e s

Key pointsKey points Socio-technical systems include computer Socio-technical systems include computer

hardware, software and people and are designed to hardware, software and people and are designed to meet some business goal.meet some business goal.

Emergent properties are properties that are Emergent properties are properties that are characteristic of the system as a whole and not its characteristic of the system as a whole and not its component parts.component parts.

The systems engineering process includes The systems engineering process includes specification, design, development, integration and specification, design, development, integration and testing. System integration is particularly critical.testing. System integration is particularly critical.

Key pointsKey points Human and organisational factors have a significant Human and organisational factors have a significant

effect on the operation of socio-technical systems.effect on the operation of socio-technical systems. There are complex interactions between the processes There are complex interactions between the processes

of system procurement, development and operation.of system procurement, development and operation. A legacy system is an old system that continues to A legacy system is an old system that continues to

provide essential services.provide essential services. Legacy systems include business processes, application Legacy systems include business processes, application

software, support software and system hardware.software, support software and system hardware.