Object-oriented task analysis

The object-oriented approach has recently received much attention in MIS development. However, as yet little research has been reported on task analysis in the object-oriented paradigm. This paper describes an object-oriented method for task analysis. Three fundamental types of objects (task, user, and interface) engaged in task analysis are described. The association between these objects is then built through identifying the messages between the objects. A practical application of this method shows that it is useful for the analysis and design of a human-computer interface.     

An integrative approach to requirements analysis: How task models support requirements reuse in a user-centric design framework

Many software systems fail to address their intended purpose because of a lack of user involvement and requirements deficiencies. This paper discusses the elaboration of a requirements-analysis process that integrates a critical-parameter-based approach to task modeling within a user-centric design framework. On one hand, adapting task models to capture requirements bridges the gap between scenarios and critical parameters which benefits design from the standpoint of user involvement and accurate requirements. On the other hand, using task models as a reusable component leverages requirements reuse which benefits design by increasing quality while simultaneously reducing development costs and time-to-market. First, we present the establishment of both a user-centric and reuse-centric requirements process along with its implementation within an integrated design tool suite. Secondly, we report the design, procedures, and findings of two user studies aimed at assessing the feasibility for novice designers to conduct the process as well as evaluating the resulting benefits upon requirements-analysis deliverables, requirements quality, and requirements reuse.     

一种安全协议的安全性分析及攻击研究

针对Web安全协议SSL的握手协议部分进行了详尽的阐述，对其安全性作了一定的分析，给出了理论上存在的三个协议漏洞的详尽描述，并且经过测试验证，指出了SSL协议存在***模式漏洞。     

Making effective use of task analysis to identify human factors issues in new rail technology

Task analysis is an important tool that enables designers to consider the human factors implications of a new technology. This paper details a task analysis for the task of driving long-haul freight trains in Australia and describes how this task analysis was used to evaluate a new in-cab information support technology. This paper then explores similarities and differences between this task analysis and one proposed by Roth and Multer (2009). It is argued that these two task analyses can form the basis for many future task analyses so that we can avoid 'reinventing the wheel,' allowing us to focus more on potential interesting differences between operations and geographical locations.     

一种自动密码协议分析方法

密码协议是构建网络安全环境、保护信息系统安全的重要手段之一,然而分析其固有缺陷和揭示入侵攻击行为,却是一件非常困难的事情。文中通过综合基于逻辑和模型检测的密码协议分析方法,提出了一种基于目标提取和消息模式匹配的自动密码协议分析方法,并以Needham-Schroeder(NS)公钥协议为例,进行了具体分析。     

Spatial ability subfactors and their influences on a computer-based information search task

OBJECTIVE: The present study examined the relationship between two distinct subfactors of spatial ability and performance in an information search task modeled on browsing the Web. BACKGROUND: Previous studies have found relationships between various measures of spatial ability and performance in a wide variety of computer-based tasks. METHOD: In the search task 101 participants (18-29 years of age) searched for the answer to a question by navigating the system. They completed the experimental task as well as a battery of cognitive ability measures that included two different measures of spatial ability. RESULTS: The results indicate that spatial orientation ability was related to performance with tasks that were high in their navigational requirement (engendered by the use of a novel aid), whereas spatial visualization was unrelated to performance in any task condition. CONCLUSION: A closer inspection of the cognitive requirements of a task may reveal what interventions could be most useful when designing computer systems or developing training programs. APPLICATION: Given the unique differences between the different spatial abilities, the current results suggest the design of navigational aids that place less demand on spatial orientation ability.     

Factors limiting the development of task analysis

Abstract

This paper sets out to summarize the current status of task analysis. There is a lack of consensus over terminology. Approaches have emerged from different theoretical and methodological sources and have been developed in different applications contexts. This has lead to a great variety of approaches, which have been used at different stages of analysis and have been given various names. Strategies for improving this situation are suggested, as are criteria for assessing approaches. The need to progress towards a well-established methodology is evident, but it is seen as a long-term goal.     

Cognitive simulation as a tool for cognitive task analysis

Cognitive simulations are runnable computer programs that represent models of human cognitive activities. We show how one cognitive simulation built as a model of some of the cognitive processes involved in dynamic fault management can be used in conjunction with small-scale empirical data on human performance to uncover the cognitive demands of a task, to identify where intention errors are likely to occur, and to point to improvements in the person-machine system. The simulation, called Cognitive Environment Simulation or CES, has been exercised on several nuclear power plant accident scenarios. Here we report one case to illustrate how a cognitive simulation tool such as CES can be used to clarify the cognitive demands of a problem-solving situation as part of a cognitive task analysis.     

Relations between task and activity: elements for elaborating a framework for error analysis

The notion of error, when applied to an activity or the result of an activity, implies the notion of task: it expresses the deviation between the activity and the task being considered from an angle which is judged to be relevant. The task and the activity are the object of representations for the analyst (or specialist) and for the driver. Four representations are dealt with in this paper: the task and the activity for the specialist and the task and the activity for the driver. An interpretation is proposed for these tasks, and they are illustrated using some of the work already carried out in this field. The signification of deviations between these representations is then discussed, together with the advantage of studying these deviations in order to clarify error-producing mechanisms. Analysis in terms of task and activity raises methodological and practical problems which are touched upon; it does not exclude referring to psychological theoretical frameworks to which it is worthwhile linking it. This perspective raises questions which make it possible to enhance the study of errors: it could be completed at a later date by extending it to include other representation categories.     

The role of task analysis in capturing requirements for interface design

Recently, the role of task analysis in design has been brought into question. It has been argued, for example, that task analysis leads to the non-creative redesign of existing artefacts. In this paper. we offer a view of task analysis that resolves this problem. In particular, we argue that by focusing upon the analysis of user/operator goals rather than an existing task implementation, task analysis encourages novel and apt design. A reformulation of hierarchical task analysis is offered, based on the sub-goal template (SGT) scheme. The SGT scheme provides a notation for goal-oriented task analysis and defines an appropriate level at which task analyses can inform the design process without constraining it to existing task implementations. The SGT scheme is compared with the systems analysis-based design methodology SSADM and the advantages of each approach are reviewed.     

Technical Note: The use of mirrors during an assembly task: a study of ergonomics and productivity

Industrial assembly tasks often require awkward, sustained neck and/or shoulder postures that can lead to increased musculoskeletal discomfort and reduced productivity. The aim of this study was to investigate the effects of mirror and periscope visual aids as ergonomic interventions designed to eliminate awkward postures of the cervicobrachial region during assembly tasks. Participants simulated a simple assembly task by using a cordless screwdriver to drive screws into a pre-tapped aluminium block. Trials of 15 min were run for each of four distinct assembly workstation configurations: industry standard (in-line screwdriver, work at elbow height, no visual aid); pistol grip (pistol grip screwdriver, work at shoulder height, no visual aid); mirror (in-line screwdriver, work at elbow height, single mirror visual aid); and periscope (in-line screwdriver, work at elbow height, two-mirror visual aid system). Muscular activity, discomfort, body posture, productivity and operator subjective assessment were recorded to determine the effects of the visual aid interventions. The results show that when comparing the interventions to the industry standard condition, there was a 45% reduction in average cervical erector spinae activity, a 90% reduction in average neck flexion angle and a 72% reduction in neck discomfort with the interventions. When comparing these interventions to the pistol grip condition there was an 80% reduction in activity of the dominant side deltoid, a 92% reduction in shoulder flexion angle and an 81% decrease in shoulder discomfort with the interventions. Productivity was greatest in the industry standard configuration followed by the pistol grip (9% lower), the periscope (13% lower) and the mirror (23% lower) configurations. A follow-up study that compared the productivity of the periscope configuration with that of the industry standard configuration showed that within a 4-h work period this productivity differential decreased by over 33%.     

A field-based versus a protocol-based approach for adaptive task assignment

Task assignment in multi-agent systems is a complex coordination problem, in particular in systems that are subject to dynamic and changing operating conditions. To enable agents to deal with dynamism and change, adaptive task assignment approaches are needed. In this paper, we study two approaches for adaptive task assignment that are characteristic for two classical families of task assignment approaches. FiTA is a field-based approach in which tasks emit fields in the environment that guide idle agents to tasks. DynCNET is a protocol-based approach that extends Standard Contract Net (CNET). In DynCNET, agents use explicit negotiation to assign tasks. We compare both approaches in a simulation of an industrial automated transportation system. Our experiences show that: (1) the performance of DynCNET and FiTA are similar, while both outperform CNET; (2) the complexity to engineer DynCNET is similar to FiTA but much more complex than CNET; (3) whereas task assignment with FiTA is an emergent solution, DynCNET specifies the interaction among agents explicitly allowing engineers to reason on the assignment of tasks, (4) FiTA is inherently robust to message loss while DynCNET requires substantial additional support. The tradeoff between (3) and (4) is an important criteria for the selection of an adaptive task assignment approach in practice.     

Integrating task analysis into system design: Surveying designers' needs

The authors are presently developing tools to enable software designers to carry out task analyses (TA). The tools will support a methodology comprising techniques for carrying out task analyses and will also take account of integrating the resulting TA information into system design. To support integration and to identify the requirements for TA tools, a group of designers were surveyed. The survey identified how the designers approach design, whether the designers believe TA would be of use to them and how, why and where TA might contribute to design. Finally the designers' views of the desired characteristics of TA tools was sought. This paper outlines the results of this small, detailed survey of what designers want, need and expect from TA tools.     

Why advice on task selection may hamper learning in on-demand education

In on-demand education, learners are required to plan their own learning trajectory by selecting suitable learning tasks. A positive effect on learning is expected when learners select tasks that help them fulfil their individual learning needs. However, the selection of suitable tasks is a difficult process for learners with little domain knowledge and suboptimal task-selection skills. A common solution for helping learners deal with on-demand education and develop domain-specific skills is to give them advice on task selection. In a randomized experiment, learners (N = 30) worked on learning tasks in the domain of system dynamics and received either advice or no advice on the selection of new learning tasks. Surprisingly, the no-advice group outperformed the advice group on a post-test measuring domain-specific skills. It is concluded that giving advice on task selection prevents learners from thinking about how the process of task selection works. The advice seems to supplant rather than support their considerations why they should perform the advised task, which results in negative effects on learning. Implications for future research on giving advice in on-demand education are discussed.     

SSL协议的扩展Rubin逻辑形式化分析

SSL协议是一个用于因特网上进行保密通信的实用安全协议,由于它的复杂性,很多形式化分析方法都不适合分析它[1].而适用于分析非单调密码协议的Rubin逻辑,不同于大多数采用"知识"和"信念"的逻辑分析发现安全缺陷的逻辑分析方法,它完整地分析协议过程中的出现所有"动作",不但能清晰地看到SSL协议的不足,还可指出进一步完善SSL协议的方法.     

基于数据流分析的网络协议逆向解析技术

对未知网络协议进行逆向解析在网络安全应用中具有重要的意义。现有的协议逆向解析方法大都存在无法处理加密协议和无法获取协议字段语义信息的问题。针对这一问题,提出并实现了一种基于数据流分析的网络协议解析技术。该技术依托动态二进制插桩平台Pin下编写的数据流记录插件,以基于数据关联性分析的数据流跟踪技术为基础,对软件使用的网络通信协议进行解析,获取协议的格式信息,以及各个协议字段的语义。实验结果证明,该技术能够正确解析出软件通信的协议格式,并提取出各个字段所对应的程序行为语义,尤其对于加密协议有不错的解析效果,达到了解析网络协议的目的。     

基于应用任务的无线传感器网络MAC协议

本文将WSN中所有节点都看作处于不同层次的sink节点,通过对网络应用语义性描述得到任务模型,将其作为传感器节点传输及处理的基本单位,就此提出了一种基于任务(Task-based,TB)的混合MAC协议。TB-MAC中簇头(上层sink)首先广播任务,接收到广播且能部分或全部完成任务的节点采用竞争方式发送应答,簇头确定参与任务执行的节点及子任务要求并确定各节点的TDMA发送时序。由于簇头进行了任务协商,使得参与任务的节点能够有效地去除节点数据间的冗余性,提高网络的性能。仿真结果显示,TB-MAC的能耗和时延性能较典型的S-MAC、Z-MAC以及ECR-MAC均有较大改善。     

No interference of task complexity with circadian rhythmicity in a constant routine protocol

Time course in task performance has been studied extensively. In particular, the investigation of circadian rhythmicity in task performance that varied in complexity. However, these studies disclosed heterogeneous outcomes. This could be the result of confounding exogenous factors, the use of diverse tasks, as well as accumulating sleepiness interfering with the underlying circadian drive. The present study varied task demands systematically within a single task and a dual task, using a constant routine protocol to examine the unmasked influence of the endogenous circadian oscillator on the periodicity of performance. Moreover, the subjects were divided into an early-start and a late-start group to estimate the potential interaction of circadian rhythmicity with the duration of prior wakefulness. The results revealed a distinct congruence in the circadian rhythms of all performance measures, with which prior wakefulness (<?40?h) did not interact. Also, single-task as well as dual-task complexity did not interfere with circadian rhythmicity. In conclusion, when sufficiently controlled for masking exogenous factors, task complexity is removed from the underlying circadian rhythms.     

Distributed temporal logic for the analysis of security protocol models

The distributed temporal logic DTL is an expressive logic, well suited for formalizing properties of concurrent, communicating agents. We show how DTL can be used as a metalogic to reason about and relate different security protocol models. This includes reasoning about model simplifications, where models are transformed to have fewer agents or behaviors, and verifying model reductions, where to establish the validity of a property it suffices to consider its satisfaction on only a subset of models.We illustrate how DTL can be used to formalize security models, protocols, and properties, and then present three concrete examples of metareasoning. First, we prove a general theorem about sufficient conditions for data to remain secret during communication. Second, we prove the equivalence of two models for guaranteeing message-origin authentication. Finally, we relate channel-based and intruder-centric models, showing that it is sufficient to consider models in which the intruder completely controls the network. While some of these results belong to the folklore or have been shown, mutatis mutandis, using other formalisms, DTL provides a uniform means to prove them within the same formalism. It also allows us to clarify subtle aspects of these model transformations that are often neglected or cannot be specified in the first place.     

改进型Helsinki协议的串空间模型分析

Helsinki协议是ISO/IEC DIS 11770-3 中提出的重要认证协议,由于协议受到来自内部的攻击,Mithcell-Yeun对其进行了改进.但改进后协议的安全性仍未得到确认,为了验证改进协议是否满足其安全目标,利用串空间模型对协议进行了建模和分析.通过分析极小元所在串与其它串的关系说明协议的一致性,通过对理想的分析说明协议的保密性.结果表明改进型协议满足其安全要求,原协议存在安全缺陷的原因是最小元可能存在M1串上,这为 Mithcell-Yeun的改进提供了理论的证明与依据.