These case studies demonstrate that work domain analysis can be used to address a range of problems beyond interface design, such as team design, training, and the evaluation of system design concepts. They also provide concrete illustrations of the guidelines for work domain analysis. Without an appreciation of the variety of applications of work domain analysis, and its suitability for implementation in industrial settings, the benefits of this approach may not be fully realized. This book supplies the deep knowledge of this tool that will lead both to more powerful and innovative applications of the approach and to designs that support flexibility or adaptation in the workplace, making systems safer, healthier, and more productive for workers.
Why Decompose? Theme 2: What Are the Project Restrictions? Theme 3: What Are the Boundaries of the Analysis? It continues with the theme of her previous published material in adding valuable explanation of the works of Rasmussen and Vicente, along with insightful expansions. We provide complimentary e-inspection copies of primary textbooks to instructors considering our books for course adoption. Stay on CRCPress. Exclusive web offer for individuals on all book. Preview this Book. Add to Wish List. Close Preview. Maintaining mother's health is the shared purpose between the obstetrical team, the anaesthesiologist, and the circulating nurse.
Maintaining baby's health is the shared purpose between the paediatric team and the circulating nurses. Pain management is shared by everyone except the scrub nurse as the scrub nurse is only responsible for managing surgical tools in the operating room OR. Everyone on the surgical team is expected to contribute in a timely treatment, appropriate treatment, and quick and safe delivery.
Mother assessment is the shared process between the obstetrical team, anaesthesiologist, and the circulating nurses. Surgery is the shared process between the obstetrical team, the anaesthesiologist, and the scrub nurse. Baby assessment is the shared process between the paediatric team and the circulating nurses. Team ConTA can reveal information flow between team members during key tasks, making it one of the most practical analyses in a Team CWA.
We examined different control tasks in various routine situations and built the decision ladders Rasmussen, Pejtersen, and Goodstein to analyse what needs to be done for each task. For example, Figure 2 left shows the decision ladders for newborn evaluation in a routine situation. The paediatric team and circulating nurses contribute to this control task. Steps are numbered for simplicity. The shaded boxes show the decision ladder elements that are activated in the situation. The baby's arrival Step 1 in the figure is a signal for the paediatric team to immediately start the assessment process Step 2.
The outcome of this activity is a set of measured data Step 3. Based on the collected information, the paediatric team identifies whether the baby is healthy or needs special care Step 4. In a routine situation, when the baby is healthy, the paediatric team knows that they need to document the results of the baby assessment Step 5 , they formulate the procedure to complete the assessment Step 6 and identify the sequence of actions to perform Step 7.
After that, the paediatric team and the circulating nurses are ready to implement the actions Step 8. The ladders in Figure 2 are typical of a traditional ConTA. In an emergency situation, there is no direct link between the state identification and the list of tasks. Figure 2 right shows the decision ladder in the case of an emergency.
By using this approach, one can clearly see that the emergency situation takes the team from routine procedures and requires the team to diagnose a more complex situation and evaluate available options, all while under time stress. While this is useful, it can also be useful to explore the roles and actions of the various team members involved in the tasks. Decision ladder for newborn evaluation in a routine situation left and in an emergency right. Team ConTA improves on the decision ladder by showing interactions between team members through the decision wheels Figure 3.
Each wheel shows a team with each team member comprising a portion of the wheel. The decision ladder of each team member is drawn within the slices and the connections between the ladders represent the interactions between team members. Synchronous and asynchronous activities are highlighted as well as communication flows between the teams and team members. Links are numbered for simplicity. Similar to Figure 2 , the typical decision ladder, once the baby has arrived, the paediatric team starts the initial observation to make sure the baby is healthy Link 1.
The circulating nurses help to complete the baby assessment Link 3. The circulating nurses share the observation task with each other Link 4 and then they plan the sequence of actions to complete that task Link 5. After completing the observation, one of the circulating nurses, Circ1, updates the paediatrician with the requested information Link 6 and the paediatric team decides if the baby needs special care Link 2. The decision wheel allows individual decision ladders to be displayed, showing team member roles.
The wheels show the decision steps taken by teams as a unit. Interactions between individuals and teams can be shown. The overall depiction of teamwork is much richer than in a decision ladder alone. In contrast to other approaches with multiple decision ladders, the decision wheel is more scalable. While the decision wheels are a good representation to show how different parties interact on a single control task, the CAT Naikar et al.
For these reasons, we consider the CAT to be another useful representation for exploring team cognitive work. Figure 4 shows the modified CAT for the surgical team. Work situations are shown along the horizontal axis and roles and responsibilities are shown along the vertical axis. The ovals indicate the teamwork functions and the small solid circles attached to the teamwork functions indicate the surgical team members that contribute to that function. The extended CAT can be used to identify the team functions at each situation. Fo example, in the newborn evaluation situation, two team functions can be identified: 1 baby assessment, which is a shared function between the paediatric team and the circulating nurses; and 2 surgery, which is the shared function between the obstetrical team, the anaesthesiologist, and the scrub nurse.
Figure 4 shows a summary of the work functions for the C-section surgery and represents how individuals are involved in multiple control tasks considering various situations. Team ConTA can show the various task steps in different control tasks, where complexities lie, and through the decision wheels, how teams coordinate their activities, and timing to accomplish joint tasks.
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Collecting the required information for the baby assessment. The paediatric team and both circulating nurses contribute to this activity. Identifying whether the baby needs special care. The paediatric team is responsible for performing this activity. Formulating a list of steps for documenting the baby's health parameters. In this situation, the scrub nurse manages the surgical tools and the circulating nurse checks the OR equipment. All the work functions in this situation are individual work functions. Patient assessment is the shared function between the obstetrical team, the anaesthesiologist, and the circulating nurses.
Patient teaching is the shared function between the anaesthesiologist and the circulating nurses. Surgery is the shared function between the anaesthesiol ogist, the obstetrical team, and the scrub nurse. Surgery is the shared function between the obstetrical team, the anaesthesiologist, and the obstetrical team and the scrub nurse.
Surgery is the shared function between the obstetrical team, the anaesthesiologist, and the scrub nurse.
Managing surgical tools is the individual work function for the scrub nurse. The rest of the team help to transfer the patient to the recovery room. Operation is done at this point. StA identifies different options that can be triggered by different situational factors. An StA may look at different task pathways that may occur Burns, Enomoto, and Momtahan , different functional configurations of the work domain that could be utilised the operating configurations of DURESS as discussed in Vicente , or, in the case of teams, different team configurations.
For the Team StA, we built an IFM to examine routine and emergency situations in a paediatric case as there are distinctly different task pathways in these two situations. This is shown in Figure 5.
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We also looked at team configurations in the routine and emergency situations. In Figure 6 we have shown the coordinative structure under routine situations, and below in emergency situations. In the emergency situation, there is tighter coordination and stronger central coordination through the emergency paediatric team leader.
Considering the paediatrician as the team lead, the whole team can be examined as an autocratic structure. Considering the emergency paediatric team and connections with every other team member, it is a distributed structure. The paediatrician and the emergency paediatric crew identify what sort of special care is needed.
The emergency paediatric team identifies the best special care that fits the situation. The emergency paediatric team decides what needs to be done to provide that special care. In case of an emergency, all of the on-call emergency paediatric team members are expected to be present in the OR within two minutes. The paediatric team should identify the reason for the emergency call and, then, identify a set of options to deal with the situation. With the help of the emergency paediatric team, the paediatrician compares the options and decides about the required special care for the baby.
The circulating nurses finish the baby assessments and update the paediatric team with the results. The paediatric team identifies that the OR forms should be filled with the results of the baby assessment. Once the baby is born, the paediatric team starts the initial observation to make sure the baby is healthy. In some cases, the paediatrician may ask the circulating nurses available in the OR to complete some baby assessments.
Once the measurement is done, one of the circulating nurses updates the paediatrician with the collected data. Then, the paediatric team decides on the sequence of actions to finish the process. A Team CWA supplements this by examining the social competencies that are equally as important in having an effective team. Table 4 presents the SRK inventory and Table 5 presents the social competencies. In Table 6 , we show how WCA can be supplemented.
Specialist: single-minded, self-starting, dedicated to provide knowledge and skills in rare supply. Team worker: cooperative, perceptive, and diplomatic. Should be able to listen, build, and avert friction. Coordinator: confident, a good chairperson, should be able to clarify goals, promote decision-making, and delegate well. As an additional perspective on CWA, Team CWA offers promise for revealing team-related information that is important in complex team situations in healthcare. There are several key benefits obtained by performing a Team CWA. By looking at which team members use which parts of the work domain, it can quickly be seen if team members must share the same object.
These objects also require careful coordination so that they are available to the right person at the right time.
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A boundary object is a concept from Activity Theory Star and Grisemer ; Bodker that describes an artefact that moves between different communities. Boundary objects often present unique design challenges in that they must be designed to be compatible in different activity systems and in collaborative work environments, for different team members, or for different teams entirely Broberg, Andersen, and Seim Deeper in the concept of boundary objects is the notion that the object itself interacts with the community boundaries to reduce or reinforce that boundary Lee Clearly in this sense, identifying boundary objects in the work domain has an influence on teamwork itself.
While Team WDA can also be used to identify the boundary objects and the shared elements of the information space, Team ConTA can be used to identify the distribution of workflow to different team members. When teams collaborate and have pressing individual goals, it can be difficult to keep focused on the overall picture.
Reinforcing shared values and purposes can be a helpful way to keep a team working together. The decision wheel allows the team's actions on a task to be mapped explicitly to each team member. When team members work together, good coordination is needed. However, by identifying when asynchronous tasks occur, communication needs and record-keeping requirements may be noted.
As the work context changes, team structures change, as seen in the StA presented here. This is clearly seen in routine and emergency situations, but could be seen in other situations as well. For example, busy periods versus quiet periods, day shifts versus night shifts. The value added by Team Strategies lies in understanding different ways to carry out shared tasks. While operational strategies focus on different ways of performing control tasks, coordination strategies examine coordination structures and the processes underlying coordination. Merely looking at functional competencies will not result in an effective team.
In an effective team some members must be leaders, some must take direction well, some must be fluent communicators. While CWA is showing promise as a method for understanding work in healthcare situations, using CWA with an explicit team perspective can reveal additional constraints relevant to teamwork. The intention of this work is not to create a new CWA, per se, but rather to suggest that CWA remains relevant in team situations and the existing framework can be usefully interpreted to understand cognitive work in teams.
In particular, we have demonstrated the Team CWA approach in the context of work models for a birthing unit. The authors thank the nursing leaders of the birthing unit for coordinating and smoothing the data collection process, and the study participants. National Center for Biotechnology Information , U. Published online May Stakeholder requirements are expressed in terms of the needs, wants, desires, expectations, and perceived constraints of identified stakeholders.
Scenarios are used to analyze the operation of the system in its intended environment and to identify requirements that may not have been formally specified by any of the stakeholders, for example, legal, regulatory, and social obligations. The context of use of the system is identified and analyzed. Included in the context analysis are the activities that users perform to achieve system objectives, the relevant characteristics of the end-users of the system e. The social and organizational influences on users that could affect system use or constrain its design are analyzed when applicable.
Identify the interaction between users and the system. Usability requirements are determined, establishing, as a minimum, the most effective, efficient, and reliable human performance and human-system interaction. When possible, applicable standards, for example ISO series, and accepted professional practices are used in order to define 1 physical, mental, and learned capabilities; 2 workplace, environment, and facilities, including other equipment in the context of use; 3 normal, unusual, and emergency conditions; and 4 operator and user recruitment, training, and culture. Define each function that the system is required to perform and how well the system, including its operators, is required to perform that function.
Define technical and quality in use measures that enable the assessment of technical achievement. Establishing high-level usability requirements that can be tested provides the foundation for a mature approach to managing usability in the development process. But while procedures for establishing these requirements are relatively well established in standards, they are not widely applied or understood, and there is little guidance on how to establish more detailed user interface design requirements.
With most emphasis in industry on formative evaluation to improve usability, there is often a reluctance to invest in the summative evaluation in the final development of the project. Formal summative evaluation in terms of established usability criteria is needed to determine valid usability. As much of systems development is carried out on a contractor-supplier basis even if the supplier is internal to the customer organization , it is for the contractor to judge whether the investment in establishing and validating usability requirements is sufficient to justify the associated risk reduction.
Usability requirements can also provide significant benefits in clarifying user needs and providing explicit user-oriented goals for development, even if they cannot be exhaustively validated. If there are major usability problems, even the results from testing three to five participants would be likely to provide advance warning of a potential problem for example, if none of the participants can complete the tasks, or if task times are twice as long as expected.
Among the questions that arise when facing the design of a new system are the following: What functions will need to be accomplished? What will be automated, and what will be performed by people? If people will be involved, how many people will it take, and what will be their role? What information and controls should be made available, and how should they be presented to enhance performance? What training is required? One approach to answering these questions is to start with a list of the tasks to be accomplished and perform task analyses to identify the sequence of actions entailed, the information and controls required to perform those actions, and the implications for number of people and training required.
This approach works well when the tasks to be performed and conditions of use can be easily specified a priori e. However, in the case of highly complex systems e. Work domain analysis techniques have been developed to support analysis and design of these more complex systems, in which all possible tasks and situations cannot be defined a priori.
Work domain analysis starts with a functional analysis of the work domain to derive the functions to be performed and the factors that can arise to complicate performance Woods, The objective is to produce robust systems that enable humans to effectively operate in a variety of situations—both ones that have been anticipated by system designers and ones that are unforeseen e. Work domain analysis methods grew out of an effort to design safer and more reliable nuclear power plants Rasmussen, ; Rasmussen, Pejtersen, and Goodstein, Analysis of accidents revealed that operators in many cases were faced with situations that were not adequately supported by training, procedures, and displays because they had not been anticipated by the system designers.
In those cases, operators had to compensate for information or resources that were inadequate in order to recover and control the system. This led Rasmussen and his colleagues to develop work domain analyses methods to support development of systems that are more resilient in the face of unanticipated situations.
A work domain analysis represents the goals, means, and constraints in a domain that define the boundaries within which people must reason and act. This provides the framework for identifying functions to be performed by humans or machines and the cognitive activities those entail. Displays can then be created to support those cognitive activities. The objective is to create displays and controls that support flexible adaptation by revealing domain goals, constraints, and affordances i.
A work domain analysis is usually conducted by creating an abstraction hierarchy according to the principles outlined by Rasmussen A multilevel goal-means representation is generated, with abstract system purposes at the top and concrete physical equipment that provides the specific means for achieving these system goals at the bottom. In many instances, the levels of the model include functional purpose a description of system purposes ; abstract function a description of first principles and priorities ; generalized function a description of processes ; physical function a description of equipment capabilities ; and physical form a description of physical characteristics, such as size, shape, color, and location.
Work domain analyses do not depend on a particular knowledge acquisition method. Any of the knowledge acquisition techniques covered in Chapter 6 can be used to inform a work domain analysis. In turn, the. There are a growing number of HSI approaches that are grounded in a work domain analysis. A prominent example is cognitive work analysis Rasmussen, ; Rasmussen et al. Burns and Hajdukiewicz provide design principles and examples of creating novel visualizations and support systems based on a work domain analysis.
Applied cognitive work analysis provides a step-by-step approach for performing and linking the results of a work domain analysis to the development of visualizations and decision-aiding concepts Elm et al. These include. Each design step produces a design artifact that collectively forms a continuous design thread providing a traceable link from cognitive analysis to design.
Work-centered design Eggleston, ; Eggleston et al. Used with permission of Lawrence Erlbaum Associates. The shared representation produced as output from a work domain analysis is typically a graphic representation of domain goals, means, and constraints. Figure provides an example of a graphic work domain representation that was developed for a nuclear power plant design.
The work domain representation specifies the primary goals of the plant generate electricity and prevent radiation release , the major plant functions in support of those goals Level 2 functions in the figure and the plant processes available for performing the plant functions Levels 3 and 4 in the figure. Level 4 specifies the major engineered control functions available for achieving plant goals.
This is the level at which manual and automatic control actions can be specified to affect goal achievement. These include alternative network representations e. Work domain analyses complement more traditional task analysis approaches. Traditional task analyses model how tasks in a domain are performed or should be performed. Work domain analyses model the problem space in which reasoning and action can take place. The work domain representation provides the basis for deriving the information required to enable domain practitioners to understand and reason about the domain at different levels of abstraction, ranging from domain purposes e.
The output of a work domain analysis is used to inform further analyses that feed different elements of human-system integration. Table provides a summary of the major elements of a cognitive work analysis that provide traceable links between the results of the work domain analysis and implications for system design, including function allocation decisions, team and organization design, design of physical and information systems including displays, personnel selection and training, development of procedures, specification of test cases to drive system evaluation, and conduct of human reliability analyses as part of risk-based analyses.
Analyzes the purposes and physical context in which domain practitioners operate. This includes a description of domain goals, means available for achieving those goals, and constraints e. Identifies what needs to be done in a work domain. This includes a description of the work situations that can arise and the work functions that need to be performed, independent of who person or machine will perform them or the detailed strategies to be used.
Analysis of strategies for making decisions and carrying out tasks, independent of who will carry them out. Focuses on who can carry out the work, how it can be distributed or shared, and how it can be coordinated. Analysis of perceptual and cognitive requirements of workers e. Work domain analysis has been an integral part of the port security HSI work described in Chapter 5.
One recent application involved determining potential technology insertion points for cargo screening at seaports where containers move directly from ship to rail, without exiting through a truck gate. In order to evaluate this domain comprehensively, interviews were conducted with terminal operations managers, physical site maps were collected, and terminal operations walkthroughs were conducted.
The information was synthesized into descriptions of current operations at each of the terminals and rail yards, with a focus on identifying common and contrasting operational practices, speed of operations, overall time requirements for ship servicing, dwell time of containers in storage stacks, labor and equipment requirements, potential radiation portal screening choke points, and issues related to the operational impact of screening at these locations.
The findings were used to define screening concepts that would maximize threat detection while minimizing impact on commerce. One of the strengths of work domain analysis methods is their ability to drive the design of novel visualizations tailored to the demands of the work Burns and Hazdukiewicz, Successful applications range from process control Roth et al. In each case, the approach yielded novel decision support concepts that were fine-tuned to the cognitive work requirements of the domain and markedly different from traditional displays in the domain.
One example drawn from a process control application is a large wall-mounted group view display intended to enable power plant control room teams to maintain broad situation awareness of the status of the plant. The goal was to increase the ability of operators to quickly assess plant state and effectively control the plant in both normal and abnormal condition. The content and organization of the group view display was based on a work domain analysis see Figure The group view display was organized around the major plant functions that need to be achieved to maintain safety and power generation goals, and the physical processes that support them.
The objective was to enable operators to rapidly assess whether the major plant functions are being achieved and the state of active plant processes that are supporting those plant functions. In cases of plant disturbances, in which one or more of the plant goals are violated, a functional representation allows them to assess what alternative means are available for achieving the plant goals.
A formal evaluation study demonstrated that the functionally organized overview display was more effective and was preferred by operators over a more conventional overview display that utilized a physical plant mimic as the organizational scheme. Teams performed significantly better with the functionally organized overview display than the more conventional physical mimic display in identifying target events percent improvement and diagnosing plant disturbances percent improvement Roth et al. The results illustrate the value of work domain analysis in deriving the critical goals, means, and constraints in the domain that impact decision making and in generating novel displays that effectively communicate these factors to support individuals and teams.
Work domain analyses promote design of novel visualizations that enable practitioners to readily apprehend and assimilate domain information. FIGURE Schematic representation of a wall-mounted group view display for a compact power plant control room derived from a cognitive work analysis approach. One recent example is a work-centered support system visualization that was developed to support dynamic mission replanning in a military airlift organization Roth et al.
A work domain analysis identified domain factors that enter into and complicate airlift mission planning decisions, including the need to match loads to currently available aircraft, obtain diplomatic clearance for landings in and flights over foreign nations, balance competing airlift demands, and conform to airfield and aircrew constraints.
Although existing information systems included all the relevant data, operational personnel had to navigate across multiple tabular displays to extract and mentally collate the necessary information. A formal evaluation comparing performance with the timeline display to performance with the legacy system established significant improvement in performance with the timeline display Roth et al.
Hypothesis and Theory ARTICLE
A work domain analysis is usually performed at several levels of detail, depending on the stage of system development and complexity of the system being analyzed. A work domain analysis is performed as a preliminary analysis to identify information needs, critical constraints, and information relationships that are necessary for successful action and problem management within the domain.
As the design evolves, the work domain analysis can be deepened and used to inform display design, function identification and allocation decisions, team and organization design, as well as identification of knowledge and skills e. The application of work domain analysis throughout the HSI design cycle has been successfully illustrated by Neelam Nakar and her colleagues, who have been applying work domain analysis and cognitive work analysis methods to the design of a first-of-a-kind Australian AWACS-style air defense platform called the Airborne Early Warning and Control Naikar and Sanderson, , ; Naikar et al.
Their work has demonstrated the usefulness of work domain analysis throughout the system design cycle, including:. Evaluation of alternative platform design proposals offered by different vendors. Work domain analyses have been similarly successfully employed to provide early input into the HSI issues in a number of large-scale first-of-a-kind projects, including the design of a next-generation power plant Roth et al.
A primary strength of work domain analysis is in emphasizing the importance of uncovering and representing domain characteristics and constraints that impact cognitive and collaborative work, as well as in guiding the design of systems that are fine-tuned to supporting the work demands and enabling domain practitioners to respond adaptively to a broad range of situations. It complements traditional sequential task analyses approaches by providing explicit shared representation of domain goals, characteristics, and constraints Miller and Vicente, ; Bisantz et al.
A limitation of work domain analysis methods that is often pointed to is that it can be resource-intensive to exhaustively map the characteristics and constraints of a domain. However, as multiple projects have shown, it is not necessary to perform an exhaustive domain analysis to reap the benefits e. A work domain analysis can be performed at different levels of detail, depending on the complexity of the system being analyzed and the phase of analysis. A preliminary, high-level work domain analysis can be performed early in the HSI process to identify information needs, critical constraints, and information relationships that are necessary for successful action and problem management in the domain.
As the design evolves, the work domain analysis can be elaborated. A related strength of work domain analysis methods is that it encourages explicit links between analysis and design via intermediate design artifacts. As the design evolves, these artifacts can be expanded and modified to provide a tracable link between domain demands, cognitive and performance requirements, and system features intended to provide the requisite support.
One of the current gaps that limit the impact of work domain analysis methods is the paucity of computational tools to facilitate analysis and serve as a core living repository of domain knowledge that could be drawn on throughout the system life cycle. While there has been some progress on. One of the most common issues that arise in complex system design is estimating whether the aggregate workload associated with the tasks assigned to system users will result in too much to do in the time available, leading to stress, unreliable performance, or, in some cases, system failure.
Workload comes in different varieties and may be assessed from many different perspectives. For tasks involving significant physical effort, physical workload is an ergonomic issue and in sustained task performance is usually measured in terms of oxygen consumption, or heart rate.
Prediction of physical workload depends on having measurement results from other related activities and conditions and estimating the differences between the known results and the postulated activity. Guidelines are available to assess excessive physical workload. Structurally, the human limbs and eyes can be directed to only one location at a time, and excessive workload can result from a requirement that they be directed to too many places for the time available or that they need to be in different places at the same time.
Speech communication is similarly limited. Assessing this kind of structural interference requires estimates or measurements of the time required for the various activities required of the limbs, eyes, and voice in each task, laying them out in sequence, subject to temporal constraints, and evaluating the potential conflicts. The most challenging evaluation is of mental workload. Humans can generally direct their attention to only one task or activity at a time.
Work Domain Analysis: Concepts, Guidelines, and Cases
That is not to say that one cannot sometimes process, to some level of completeness, multiple streams of information, especially when they are coordinated or relate to the same task. There is a large literature on attention, attention management, and multitasking that is beyond the scope of this report see, for example, Chaffin, Anderson, and Martin, ; Wickens and Hollands, ; and Charlton, The distinctions among these types may become blurred. Thinking is often accompanied by visual exploration, and it is difficult to distinguish the structural constraint of where the eyes are looking from the mental load of reasoning about what is seen.
Demanding physical effort may capture attention that could otherwise be directed to cognitive task performance. Most depend on having the results of a detailed task analysis, requiring an understanding of the cognitive components of the task and estimates of the time that will be associated with each task element. McCracken and Aldrich defined the visual, auditory, cognitive, and perceptual-motor load associated with a collection of common elemental tasks, such as reading an instrument or operating a control. Then, after making corresponding estimates of the time required for each task element in context, they used task analysis results to bring together the elemental components into estimates of the aggregate loads as a function of time on each modality.
This basic approach has also been used in a variety of modeling contexts, including network models and more detailed human performance simulations Laughery and Corker, When prediction is not possible or leads to uncertain results, it is necessary to undertake a study to estimate mental workload from actual measurements. There are fundamentally four kinds of measurements and analysis that have been used: 1 varying the task load corresponding to the range of expected task conditions e. There are numerous summary references that document these methods, such as Tsang and Wilson and Hancock and Desmond When individual tasks are time sensitive or when the system users are subjected to the demands of multitasking, excessive workload is one of the paramount issues that can degrade system performance.
Whenever a new system is designed or revised, it is important to consider the impact of the design on user workload. Workload estimates are also needed in job design—the assembly of tasks into jobs. Workload is a key component in preparing estimates of needed manpower or, when there is a mandate to reduce staff, workload estimates are the most important consideration. Ultimately, workload is reflected in the personnel requirements forecast. It is an important area for coordination across the HSI domains.
The primary shared representations are graphs of workload as a function of time or task progress and PERT charts a network diagram in which milestones are linked by tasks or Gantt charts bar charts that illustrate a project schedule. These shared representations illustrate the timelines of activities, showing where overlaps occur, with highlights showing phases in which the workload exceeds limits.
For descriptions of these tools, see Modell However, in most cases the output of studies assessing workload is expressed in an experiment report.
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Whenever possible the estimated workload should be compared with acceptable limits. In a typical system design, consideration of workload begins with the initial task analysis and context of use assessment. In early stages, the estimates will be largely qualitative. The aspects of the design are identified that may be workload sensitive or where overload presents substantial task completion or safety risk.
Work Domain Analysis Concepts Guidelines And Cases 2013
As the design matures, the workload estimates should become more quantitative, and confidence in the estimates will improve. When designs have reached the stage of completion in which a simulation of the task or of alternative task designs can be built, modeling studies or human-in-the-loop evaluations can be undertaken to estimate the workload of critical phases of the operation or critical elements of the system see the section below on models and simulations. These studies will contribute to the manpower and personnel domains as well and should be coordinated with specialists in those areas.
Measuring workload is also important during summative test and evaluation stages of a project. The definition, measurement, and prediction of workload, particularly mental workload, has been on the human factors research agenda for more than 30 years. Measurement protocols and modeling approaches are available. It is much harder to define acceptable limits, because these are dependent on the measures used and there is no standardization of the measures, at least for mental workload.
Using them requires the expertise of human factors professionals. All of the methods provide only approximate answers until the full system design is complete and the workload of using the real system can be evaluated. Objective measures are usually to be preferred, but they require more effort to instrument and apply to simulated or real task performance. Subjective methods have been shown to be reliable if standardized question-. Users can report only their perceptions and, under stressful conditions, perceived workload may be more important than objective workload requirements.
There is a need for more collaboration among the specialists of the manpower, personnel, and human factors domains to ensure that the studies that are undertaken meet the requirements of all these stakeholders. Suitable shared representations are not well developed.
Workload models can produce PERT chart—like representations that are useful for detailed analysis of operational concepts, but the output of most workload studies is simply an experiment report. New visualizations are required that are grounded in data but that present it in a form that allows all stakeholders to understand not only what the recommendations are, but also how they are supported by the data. The preceding sections of this chapter have emphasized design as conducted by professional designers and engineers. This section focuses on design as a hybrid activity see, e.
Much of the background for these concepts was provided in the participatory analysis section of Chapter 6. We restrict the discussion here to design-related concepts within that more general framework. The principal focus of participatory design has been twofold Blomberg et al. This overall philosophy means that end-users are more involved in design and development than is the case in conventional treatments, in which end-users tend to be consulted during requirements elicitation, and again during usability or acceptance testing.
By contrast, participatory design typically involves iterative engagements with users as first-class participants at multiple, strategically chosen moments during the specification-design-evaluation processes. When appropriate, this approach supplements the knowledge of engineers and professional designers with the work domain. Participatory design work has focused on issues of theory, context, and practice for a summary, see Levinger, The analysis phases of scenario-based methods are noted in the previous chapter Carroll, , ; Carroll, Rosson, and Carroll, b, These activities continue in design.
One of the strongest ways to describe a revised or new design is through a story of that design in use. Scenario-based design is based around such stories. Scenario-based design builds on the problem statement through the following steps:. A set of activity designs literally, action-oriented scenarios of future use are constructed and evaluated with end-users. The claims from the previous step i. An information design is proposed, based on the approved activity designs. Each activity design becomes a reference model for the evaluation of each information design.
The information design provides a more detailed perspective on the narrative of the activity design, and is itself a more refined scenario of future use. Again, the claims from the participatory analysis can be used to structure the evaluation. A more detailed interaction design is developed, based on a refined and stabilized information design.
Each interaction design is an even more refined and developed scenario of future use. The action designs remain the reference models against which the interaction design is evaluated—again with the potential aid of the claims from the participatory analysis. In these ways, scenario-based design produces a structured series of narratives, each focused on resolving particular questions.
The scenarios remain intelligible and accessible to the end-users, who are encouraged to critique and modify them as needed. Another powerful way to tell a story about future use is through enactment of that scenario using tangible materials, such as prototypes of the envisioned technology. If the technology has been completed, then this approach becomes a matter of formative or summative usability evaluation see Chapter 8.
However, in participatory design, the prototype is often left strategically incomplete to encourage and even to require users to contribute their ideas directly to the evolving concept. This approach has several advantages. Second, it is easy to modify in place—a form of user-initiated design. Thus, a low-tech representation becomes another means for leveling the playing field, encouraging end-users to make egalitarian contributions of their knowledge to complement the knowledge of software and design professionals. Muller provided an evolutionary view of paper-and-pencil materials and associated working practices in the design of user interfaces.
Low-tech representations have the additional advantage of being a form of literal requirements document. That is, the constructed form of the representation is a first approximation of the intended final design of the user interface. In the course of working with the low-tech representation, users and systems professionals usually enact or review one or more. Note that the use of low-tech materials for design is quite different from the use of low-tech materials for evaluation, as advocated in contextual inquiry and design Holtzblatt, ; Holtzblatt et al.
These latter approaches describe the use of a low-tech prototype as a valuable proxy for a functioning system in usability testing. In participatory design, the goal is for the users to contribute as peer co-designers, not simply as evaluators. The sequence of events in this scenario often captured in the form of a video recording—e.
In these ways, the simple paper-and-pencil or cardboard materials can become powerful engines for explicating and enhancing designs. The strategy of acting out a use scenario has been another tool of participatory design. The principal method in information technology e. A secondary method in information technology e.
Ethnography has figured prominently in the literature on participatory design e. The specific methods used by ethnographers in design activities tend to invoke other methods, previously described in the section on participatory design. For broader discussions of ethnography, see Chapter 6. Preceding sections have described the use of stories and scenarios, low-technology representations, and user-produced documentaries as methods.
These and other methods have been integrated in the generative workshops of Sanders and colleagues Sanders, Generative workshops consist of methods from market research e. Each participatory design method produces its own characteristic shared representation and contribution; several of these were reviewed in the preceding chapter on analysis. Table provides a summary of contributions and shared representations. Layered design documents activity design, information design, interaction design. In brief recapitulation, scenario-based methods may produce stories, storyboards, narratives, and use cases; the latter are particularly useful for systems engineering.
These materials can become background or reference material for the more detailed work of designers and developers. Alternatively, a more detailed scenario can develop into use cases, which directly inform design and development on an event-by-event or action-by-action basis. Low-technology representations provide first drafts of user interface designs and are suitable inputs to the work of professional designers; the information surrounding them is valuable to resolve questions that designers and implementers might have about why certain features are needed and for what purpose.
In addition to the first draft approach, low-technology representations can become detailed design documents, ready for implementation into working hardware or software. The theatrical methods are similar to the multimedia documentary methods in the preceding chapter.
As with the narratives and explanations surrounding a low-technology representation, the additional information in a theatrical method may provide useful contextualization of design recommendations and implementation decisions. The workshop methods are similar in outcome to the theatrical methods, with the difference that the workshop methods were designed by professional designers to be used by professional designers.
Their outcomes are thus structured to be useful inputs to the next, more formalized design steps. Strengths and weaknesses of participatory design are similar to those for participatory analysis, as discussed in Chapter 6. There are two principal weaknesses of the participatory approaches. The first is a matter of appearance. Participatory approaches involve knowledge holders who have historically been undervalued in systems develop-. Similarly, the strategic informality of the participatory approaches may present an appearance problem—i. In the participatory analysis section of Chapter 6 , we summarized the contextual inquiry process, including the three activities of contextual inquiry, interpretation, and affinity analysis, as well as the construction of the five models characterized, respectively, in flow, sequence, physical, cultural, and artifact terms.
Contextual inquiry can lead in turn to contextual design Holtzblatt, ; Holtzblatt et al. Iteratively refine these concepts via storyboards.