What are latent conditions and active failures?

What are latent conditions and active failures?
Ans: Inevitably, all barriers have weaknesses of some kind. Reason calls these ‘latent conditions’ as they usually only contribute to system failure when some other problem occurs. For example, a weakness of a conflict alert system is that it may lead to many false alarms. Latent conditions lead to system failure when the defenses built into the system do not trap an active failure by a system operator. The human error is a trigger for the failure but should not be considered to be the sole cause of the failure. Reason explains this using his well-known ‘Swiss cheese’ model of system failure.
In this model, the defenses built into a system are compared to slices of Swiss cheese. Some types of Swiss cheese, such as Emmental, have holes and so the analogy is that the latent conditions are comparable to the holes in cheese slices. The position of these holes is not static but changes depending on the state of the overall socio-technical system. If each slice represents a barrier, failures can occur when the holes line up at the same time as a human operational error. An active failure of system operation gets through the holes and leads to an overall system failure.

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Why are plan-driven (rather than agile) processes used in systems engineering?

Why are plan-driven (rather than agile) processes used in systems engineering?
Ans: Plan-driven processes are used in systems engineering because different parts of the system are being developed at the same time. For systems that include hardware and other equipment, changes during development can be very expensive or, sometimes, practically impossible. It is essential therefore, that the system requirements are fully understood before hardware development or building work begins.
Reworking the system design to solve hardware problems is rarely possible. For this reason, more and more system functionality is being assigned to the system software. This allows some changes to be made during system development, in response to new system requirements that inevitably arise.

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What are the main drivers for system procurement decisions?

What are the main drivers for system procurement decisions?
Ans: The drivers for system procurement decisions are:
1. The state of other organizational systems: If the organization has a mixture of systems that cannot easily communicate or that are expensive to maintain, then procuring a replacement system may lead to significant business benefits.
2. The need to comply with external regulations: Increasingly, businesses are regulated
and have to demonstrate compliance with externally defined regulations (e.g., Sarbanes-Oxley accounting regulations in the United States). This may require the replacement of noncompliant systems or the provision of new systems specifically to monitor compliance.
3. External competition: If a business needs to compete more effectively or maintain a competitive position, investment in new systems that improve the efficiency of business processes may be advisable. For military systems, the need to improve capability in the face of new threats is an important reason for procuring new systems.
4. Business reorganization: Businesses and other organizations frequently restructure\ with the intention of improving efficiency and/or customer service. Reorganizations lead to changes in business processes that require new systems support.
5. Available budget: The budget available is an obvious factor in determining the scope of new systems that can be procured.

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What are the three principal stages of systems engineering?

What are the three principal stages of systems engineering?
Ans: 1. Procurement or acquisition: During this stage, the purpose of a system is decided; high-level system requirements are established; decisions are made on how functionality will be distributed across hardware, software, and people; and the components that will make up the system are purchased.
2. Development: During this stage, the system is developed. Development processes include all of the activities involved in system development such as requirements definition, system design, hardware and software engineering, system integration, and testing. Operational processes are defined and the training courses for system users are designed.
3. Operation: At this stage, the system is deployed, users are trained, and the system is brought into use. The planned operational processes usually then have to change to reflect the real working environment where the system is used. Over time, the system evolves as new requirements are identified. Eventually, the system declines in value and it is decommissioned and replaced.

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What is a wicked problem?

What is a wicked problem?
Ans: Generally, complex socio-technical systems are developed to tackle what are sometimes called ‘wicked problems’. A wicked problem is a problem that is so complex and which involves so many related entities that there is no definitive problem specification. Different stakeholders see the problem in different ways and no one has a full understanding of the problem as a whole. The true nature of the problem may only emerge as a solution is developed. An extreme example of a wicked problem is earthquake planning. No one can accurately predict where the epicenter of an earthquake will be, what time it will occur, or what effect it will have on the local environment. It is impossible to specify in detail how to deal with a major earthquake.

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Why are socio-technical systems non-deterministic?

Why are socio-technical systems non-deterministic?
Ans: Socio-technical systems are non-deterministic partly because they include people and partly because changes to the hardware, software, and data in these systems are so frequent. The interactions between these changes are complex and so the behavior of the system is unpredictable. This is not a problem in itself but, from a dependability perspective, it can make it difficult to decide whether or not a system failure has occurred, and to estimate the frequency of system failures. For example, say a system is presented with a set of 20 test inputs. It processes these inputs and the results are recorded. At some later time, the same 20 test inputs are processed and the results compared to the previous stored results. Five of them are different. Does this mean that there have been five failures? Or are the differences simply reasonable variations in the system’s behavior? You can only find this out by looking at the results in more depth and making judgments about the way the system has handled each input.

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What are three influences on the reliability of a system?

What are three influences on the reliability of a system?
Ans: In a socio-technical system, you need to consider reliability from three perspectives:
1. Hardware reliability: What is the probability of hardware components failing and how long does it take to repair a failed component?
2. Software reliability: How likely is it that a software component will produce an incorrect output? Software failure is distinct from hardware failure in that software does not wear out. Failures are often transient. The system carries on working after an incorrect result has been produced.
3. Operator reliability: How likely is it that the operator of a system will make an error and provide an incorrect input? How likely is it that the software will fail to detect this error and propagate the mistake?

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What are emergent properties?

What are emergent properties?
Ans: The complex relationships between the components in a system mean that a system is more than simply the sum of its parts. It has properties that are properties of the system as a whole and cannot be attributed to any specific part of the system, known as ‘emergent properties’.
There are two types of emergent properties:
1. Functional emergent properties when the purpose of a system only emerges after its components are integrated. For example, a bicycle has the functional property of being a transportation device once it has been assembled from its components.

2. Non-functional emergent properties, which relate to the behavior of the system in its operational environment. Reliability, performance, safety, and security are examples of emergent properties.

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What is the difference between a technical and a socio-technical system?

What is the difference between a technical and a socio-technical system?
Ans: Technical computer-based systems are systems that include hardware and software components but not procedures and processes. Examples of technical systems include televisions, mobile phones, and other equipment with embedded software. Most software for PCs, computer games, etc., also falls into this category. Individuals and organizations use technical systems for a particular purpose but knowledge of this purpose is not part of the system. For example, the word processor I am using is not aware that is it being used to write a book.
Socio-technical systems include one or more technical systems but, crucially, also include people who understand the purpose of the system within the system itself. Socio-technical systems have defined operational processes and people are inherent parts of the system. They are governed by organizational policies and rules and may be affected by external constraints such as national laws and regulatory policies. For example, this book was created through a socio-technical publishing system that includes various processes and technical systems.

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What is the difference between the business process layer and the organizational layer in the socio--technical systems stack?

What is the difference between the business process layer and the organizational layer in the socio--technical systems stack?
Ans: At business process layer level, the organizational business processes, which make use of the software system, are defined and enacted. The organizational layer includes higher-level strategic processes as well as business rules, policies, and norms that should be followed when using the system.

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