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  4. Computer System Reliability : Safety And Usability Hardcover

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However, as Blomberg, Burrell, and Guest argued, reported behavior can be unreliable, for a host of reasons. Ethnographic studies are a type of field study that bases findings on observed, rather than reported behavior; several scholars point out the need for it to be systematic and theory based Forsythe, ; Suchman, Ethnographic approaches are useful to research on human-computer interactions because they help to address a network-based analysis of interactive relations. Savioja and Norros recognized that mediation of computer tools involves both instrumental and psychological functions in communication.

They created a questionnaire based on their understanding of those activities to investigate cooperative work through collective individual activities. For example, Schmidt and Bannon defined cooperation as dependency in work, and their understanding of systems includes people working together to accomplish a task. That insight applies to work in the maritime domain because every offshore operation needs a team of distributed operators working cooperatively with ship bridge system.

Gutwin and Greenberg 1 developed a conceptual framework for evaluating a team of operators in complex IT systems applying it to groupware. Multiple evaluators engage in the evaluation process. However, as Pinelle and Gutwin argued, the criteria of multiple evaluators and task-based analysis alone may decrease the effectiveness of this method.

As Schmidt argued, with respect to mutual critical assessment in a team of operators and computer-mediated work:. Different decision makers will typically have preferences for different heuristic approaches, strategies, stop rules, etc. This statement questions the value of using multiple evaluators in cooperative work. Inclusion of all the stakeholders would represent a shift toward understanding the process in an actor network by considering the impact of technologies on human practices. In offshore operation, when a vessel approaches oil- and gas-gathering platforms, humans operators , subsystems dynamic positioning , and artifacts paper-based forms, alarm clocks, and calculators must work together to make the tasks successful.

Therefore, analyses that involve interactive relationships in a larger system assist in illuminating a work environment in terms of a better understanding of usability issues. This literature review has aimed at sketching what we believe is a broad perspective on complex systems. As stated above, evaluation after the fact by users provides an incomplete framework. In this case study we examine the interactive relationships that structure the work situation of an offshore operation at sea as a network.

This network is dynamic in that it changes depending on the task. As the next section illustrates, the shape of this network reflects the interactive relationships between humans and nonhumans in a network and determines its functionality. This section describes an offshore dynamic positioning operation based on our fieldwork, in order to address how we can consider usability issues for a work environment where a team of operators work with both the hardware and the software of a ship bridge system and other artifacts they add to it.

The dynamic positioning operation is a fundamental function for all types of ship bridge systems, designed to maintain safety through effective positioning. The complexity that operators face includes the work conditions imposed by waves and winds. These include the threat of a collision between the vessel and the oil platform and the problem of maintaining balance for a vessel that carries balancing mechanisms using water and mud containers, and the positioning of supplies on deck. Our fieldwork was conducted on an offshore vessel in the North Sea. We observed dynamic positioning operations 20 times over the course of seven consecutive days of this offshore work with two teams on the same offshore vessel.

Each team had six people work on offshore operations with a shift change every six hours.

The operators that we observed worked in distributed locations. For example, an operator and first officer were on the bridge. The engine operator was at the bottom of the vessel. Another crew worked outside the bridge on the deck. The platform operator was on the oil and gas platform rather than on the ship. All these operators worked together. The following excerpt from a dialogue among dynamic positioning operators illustrates the interdependence of their work and the fact that operators adapt to the subsystems in order to operate them.

Usability problems are identified when the operators have to add artifacts that should have been part of the dynamic positioning subsystem. Operator 1 on the ship bridge O1 : Please report the weather, first officer verbal communication. A loud noise comes from the bottom of the vessel—the engine room—where the first officer is unable to hear clearly what the operator is saying.

O1: Check the wave and wind. This time, Operator 1 speaks loudly. Then the first officer walks to a computer, which is not part of the dynamic positioning system, turns on the display, and pulls up a weather report page.

The weather report is important because if the wave and winds are too high, all operations have to be postponed. However, such a weather report page is not part of dynamic positioning subsystem. As he speaks, he logs the information on a checklist, including the current time and place, and brings it to the operator. O1: Okay. Operator 1 then picks up one of the communication channels and speaks:. O1: Engine room, report the engine status? Engine room operator E; responding via the audio communication channel : Power is okay.

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Computer System Reliability: Safety and Usability (Hardcover)

O1: Report containers the containers are at the bottom of the vessel; engine officers usually take care of them. Please report [them] to me.

Serial and parallel reliability calculations

We observe that the system only shows the pressure of the piping tube on the ship bridge display and is too far away for Operator 1 to observe. This is a significant limitation of the ship bridge subsystem. Two added artifacts, an alarm clock and a calculator, have to be used. It also increases risk because there is no double-check procedure by another operator.

E: Pipe pressure is okay.


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He looks at the screens above his head and says:. E: [Container] one, two, three, and four are okay, but you need to pipe out water from five and take some mud from five to six. Our observations reveal that engine crews must always check the balance when conducting dynamic positioning operations to avoid capsize due to unbalanced weight on either side. O1 talking to the platform operator via the audio communication channel : I need to prepare for a while. I need to balance the ship before I operate.

Platform operator P : Okay. Call me back when you are ready. O1: Thanks. Deck crew D : Yes. Two deck crewmembers walk on deck and open the valve of the container on the left side of the vessel. Then Operator 1 records all information on the checklist that the first officer gave him. Next, Operator 1 calculates roughly how much mud he needs to move to container six see Figure 2. When he finishes his calculation, he fills out a paper form and delivers it to the first officer to sign. Figure 2.

Calculator left and alarm clock right. Photo: Yushan Pan. Operator 1 then sets a five-hour alarm on the clock see Figure 2 before he pipes out water from container five.

NFRs as Backlog Constraints

Operator 1 operates the container systems to pipe water and stops when he hears the alarm from the clock. He sets another minute alarm and starts to move mud. After that, he asks the first officer again:.

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O1: Officer, check the wave and wind again. The first officer walks to the computer again, checks and writes down the information, and speaks to Operator 1. He writes down the information again and brings it to the operator. Wind [is] five. O1: Engine, are the containers okay?

Computer System Reliability : Safety And Usability Hardcover

E via the communication channel : Checked, [they are] okay. O1 via the communication channel : Deck crew. Report the position when I am doing the dynamic positioning. Deck crew D : Okay. O1 via the communication channel : Platform, could you put down the crane? Operator 1 turns off the communication channel and speaks to the first officer.