Socio-technical systems include both technical and human elements. They are made up of interconnected layers from equipment and software to business processes and societal rules. Properties emerge from the interactions between these layers, including reliability, security, and usability. Whether a socio-technical system is considered a success or failure depends on perspective, as stakeholders have differing views and system behavior is non-deterministic due to human factors. Failures are also inevitable given the complexity of relationships in socio-technical systems.

1. Socio-technical Systems
Socio-technical systems, 2013 Slide 1

2. Systems
Software engineering is not an isolated
activity but is part of a broader systems
engineering process.
Software systems are therefore not
isolated systems but are essential
components of broader systems that have
a human, social or organizational purpose.
An embedded weather recording system is
part of broader weather recording and
forecasting systems
These include hardware and software,
forecasting processes, system users, the
organizations that depend on weather
forecasts, etc.
Socio-technical systems, 2013 Slide 2

3. The socio-technical systems
stack
Socio-technical systems, 2013 Slide 3

4. Layers in the STS stack
• Equipment
– Hardware devices, some of which may be computers. Most
devices will include an embedded system of some kind.
• Operating system
– Provides a set of common facilities for higher levels in the
system.
• Communications and data management
– Middleware that provides access to remote systems and
databases.
• Application systems
– Specific functionality to meet some organization
Socio-technicalrequirements.
systems, 2013 Slide 4

5. Layers in the STS stack
• Business processes
– A set of processes involving people and computer systems
that support the activities of the business.
• Organizations
– Higher level strategic business activities that affect the
operation of the system.
• Society
– Laws, regulation and culture that affect the operation of the
system.
Socio-technical systems, 2013 Slide 5

6. Holistic system design
• There are interactions and dependencies between
the layers in a system and changes at one level ripple
through the other levels
– Example: Change in regulations (society) leads to changes in
business processes and application software.
• For dependability, a systems perspective is essential
– Contain software failures within the enclosing layers of the
STS stack.
– Understand how faults and failures in adjacent layers may
affect the software in a system.
Socio-technical systems, 2013 Slide 6

7. Complex systems
A system is a
purposeful collection
of inter-related
components working
together to achieve
some common
objective.
A system may include
software, mechanical,
electrical and
electronic hardware
The properties and behaviour of system and be operated by
components are inextricably inter- people.
mingled. This leads to complexity.
Socio-technical systems, 2013 Slide 7

8. System categories
• Technical computer-based systems
– Systems that include hardware and software but where the
operators and operational processes are not normally
considered to be part of the system. The system is not self-
aware.
– Example: A word processor used to write a book.
• Socio-technical systems
– Systems that include technical systems but also operational
processes and people who use and interact with the technical
system. Socio-technical systems are governed by
organisational policies and rules.
– Example: A publishing system to produce a book.
Socio-technical systems, 2013 Slide 8

9. Socio-technical system
characteristics
• Emergent properties
– Properties of the system of a whole that depend on the
system components and their relationships.
• Non-deterministic
– They do not always produce the same output when
presented with the same input because the systems’s
behaviour is partially dependent on human operators.
• Complex relationships with organisational objectives
– The extent to which the system supports organisational
objectives does not just depend on the system itself.
Socio-technical systems, 2013 Slide 9

10. Emergent properties
Properties of the system as a
whole rather than properties
that can be derived from the
properties of components of
a system
Emergent properties are a
consequence of the
relationships between
system components
They can therefore only be
assessed and measured
once the components have
been integrated into a
system
Socio-technical systems, 2013 Slide 10

11. Examples of emergent properties
Property Description
Volume The volume of a system (the total space occupied) varies depending on how
the component assemblies are arranged and connected.
Reliability System reliability depends on component reliability but unexpected
interactions can cause new types of failures and therefore affect the reliability
of the system.
Security The security of the system (its ability to resist attack) is a complex property
that cannot be easily measured. Attacks may be devised that were not
anticipated by the system designers and so may defeat built-in safeguards.
Repairability This property reflects how easy it is to fix a problem with the system once it
has been discovered. It depends on being able to diagnose the problem,
access the components that are faulty, and modify or replace these
components.
Usability This property reflects how easy it is to use the system. It depends on the
technical system components, its operators, and its operating environment.
Socio-technical systems, 2013 Slide 11

12. Types of emergent property
• Functional properties
– These appear when all the parts of a system work together to
achieve some objective. For example, a bicycle has the
functional property of being a transportation device once it
has been assembled from its components.
• Non-functional emergent properties
– Examples are reliability, performance, safety, and security.
These relate to the behaviour of the system in its operational
environment. They are often critical for computer-based
systems as failure to achieve some minimal defined level in
these properties may make the system unusable.
Socio-technical systems, 2013 Slide 12

13. Reliability as an emergent
property
Because of component inter-
dependencies, faults can be
propagated through the system.
System failures often occur
because of
unforeseen inter-relationships
between
components.
It is practically impossible to
anticipate all possible component
relationships.
Software reliability measures may
Socio-technical systems, 2013 give a false picture of the overall
Slide 13
system reliability.

14. Influences on reliability
• Hardware reliability
– What is the probability of a hardware component failing and how
long does it take to repair that component?
• Software reliability
– How likely is it that a software component will produce an incorrect
output. Software failure is usually distinct from hardware failure in
that software does not wear out.
• Operator reliability
– How likely is it that the operator of a system will make an error?
• Failures are not independent and they propagate from one level
to another.
Socio-technical systems, 2013 Slide 14

15. Failure propagation
Socio-technical systems, 2013 Slide 15

16. Success and failure
Socio-technical systems, 2013 Slide 16

17. Non-determinism
• A deterministic system is one where a given
sequence of inputs will always produce the same
sequence of outputs.
• Software systems are deterministic; systems that
include humans are non-deterministic
– A socio-technical system will not always produce the same
sequence of outputs from the same input sequence
– Human elements
• People do not always behave in the same way
– System changes
• System behaviour is unpredictable because of frequent changes
to hardware, software and data.
Socio-technical systems, 2013 Slide 17

18. Success criteria
• Complex systems are developed to address ‘wicked
problems’ – problems where there cannot be a
complete specification.
• Different stakeholders see the problem in different
ways and each has a partial understanding of the
issues affecting the system.
• Consequently, different stakeholders have their own
views about whether or not a system is ‘successful’
– Success is a judgment and cannot be objectively measured.
– Success is judged using the effectiveness of the system
when deployed rather than judged against the original
reasons for procuement.
Socio-technical systems, 2013 Slide 18

19. Conflicting views of success
• A medical information system may be designed to support
multiple, conflicting goals
– Improve quality of care.
– Provide better information and care costs and so increase revenue.
• Fundamental conflict
– To satisfy reporting goal, doctors and nurses had to provide
additional information over and above that required for clinical
purposes.
– They had less time to interact with patients, so quality of care
reduced. System was not a success.
• However, managers had better reports
– System was a success from a managerial perspective.
Socio-technical systems, 2013 Slide 19

20. What is failure?
• Technical view: a failure
is ‘a deviation from a
specification’.
• An oracle can examine a
specification, observe a
system’s behaviour and
detect failures.
• Failure is an absolute -
the system has either
failed or it hasn’t
Socio-technical systems, 2013 Slide 20

21. A hospital system
• A hospital information system is designed to maintain
information about available beds for incoming patients and to
provide information about the number of beds to the admissions
unit.
• It is assumed that the hospital has a number of empty beds and
this changes over time. The variable B reflects the number of
empty beds known to the system.
• Sometimes the system reports that the number of empty beds is
the actual number available; sometimes the system reports that
fewer than the actual number are available .
• In circumstances where the system reports that an incorrect
number of beds are available, is this a failure?
Socio-technical systems, 2013 Slide 21

22. Bed management system
• The percentage of system users who considered the
system’s incorrect reporting of the number of
available beds to be a failure was 0%.
• Mostly, the number did not matter so long as it was
greater than 1. What mattered was whether or not
patients could be admitted to the hospital.
• When the hospital was very busy (available beds =
0), then people understood that it was practically
impossible for the system to be accurate.
• They used other methods to find out whether or not a
bed was available for an incoming patient.
Socio-technical systems, 2013 Slide 22

23. Failure is a judgement
• Specifications are a gross simplification of reality for
complex systems.
• Users don’t read and don’t care about specifications
• Whether or not system behaviour should be considered
to be a failure, depends on the observer’s judgement
• This judgement depends on:
– The observer’s expectations
– The observer’s knowledge and experience
– The observer’s role
– The observer’s context or situation
– The observer’s authority
Socio-technical systems, 2013 Slide 23

24. Failures are inevitable
• Technical reasons
– When systems are composed of opaque and uncontrolled
components, the behaviour of these components cannot be
completely understood
– Failures often can be considered to be failures in data rather than
failures in behaviour
• Socio-technical reasons
– Changing contexts of use mean that the judgement on what
constitutes a failure changes as the effectiveness of the system in
supporting work changes
– Different stakeholders will interpret the same behaviour in different
ways because of different interpretations of ‘the problem’
Socio-technical systems, 2013 Slide 24

25. Conflict inevitability
• Impossible to establish a set of requirements where
stakeholder conflicts are all resolved
• Therefore, successful operation of a system for one
set of stakeholders will inevitably mean ‘failure’ for
another set of stakeholders
• Groups of stakeholders in organisations are often in
perennial conflict (e.g. managers and clinicians in a
hospital). The support delivered by a system
depends on the power held at some time by a
stakeholder group.
Socio-technical systems, 2013 Slide 25

26. Normal failures
• ‘Failures’ are not just catastrophic events but normal,
everyday system behaviour that disrupts normal work
and that mean that people have to spend more time
on a task than necessary
• A system failure occurs when a direct or indirect user
of a system has to carry out extra work, over and
above that normally required to carry out some task,
in response to some inappropriate or unexpected
system behaviour
• This extra work constitutes the cost of recovery from
system failure
Socio-technical systems, 2013 Slide 26

27. Key points
• Socio-technical systems include computer hardware,
software and people and are designed to meet some
business goal.
• Human and organizational factors, such as the
organizational structure, have a significant effect on
the operation of socio-technical systems.
• Failure and success are not absolute – they are
always a judgement made from outside of the system
Socio-technical systems, 2013 Slide 27