This chapter presents a method for usability diagnosis of webpages based on time analysis of clickstream data. The resulting diagnostic reports enable website managers to learn about possible usability barriers. Different website design deficiencies are associated with different patterns of exceptional navigation. This chapter presents a method based on the integration of stochastic Bayesian and Markov models with models for estimating and analyzing visitors' mental activities during their interaction with a website. Based on this approach, a seven-layer model for data analysis is proposed and an example of a log analyzer that implements this model is presented. The chapter describes state-of-the-art techniques and tools implementing these methods and maps areas for future research. We begin with some definitions and

Abstract. Studies about the sources of critical accidents in operating human-made systems indicate that most of them are commonly attributed to errors made by the human operators. These findings motivated the development of a guide for designing and developing systems which are resilient to operational errors. This article reports on the development of such a guide by the Gordon Center for System Engineering at the Technion. Assuming the Human Factors variant of Murphy's Law, the guide applies the STAMP paradigm of self-control in scenario-based design, relying on a model of resilient operation. The guide suggests designing three firewalls, for preventing latent threats, preventing escalation and learning from incidents. The effectiveness of the guide was evaluated collaboratively in a special INCOSE_IL working group, by examination of its applicability to case studies. The guide was validated by scoring the guidelines applicability to failure modes observed in a special database of 67 mishaps. OverviewThis article documents an on-going project of the Gordon Center for Systems Engineering at the Technion. The goal of this project is to develop a guide for system engineers, with guidelines for assuring safe interaction between the operators and the machine.Section 2 describes prior studies in safety analysis which motivated the need to conceptualize system resilience. Section 3 discusses topics in resilience analysis showing the need for resilience assurance. Section 4 presents various subjects in resilience assurance, demonstrating the need for this project. Section 5 presents the project, including reference to the current version of the guide, description of the history of the guide development, example of using the guide, description of the validation method and outcome, and discussion of limitations in employing the guide. Section 6 includes suggestions for subsequent studies. Why Systems Fail?This section presents references to topics in safety analysis with focus on the role of the human operator in the system failure.There are many explanations for the source of system failures. Few of them are:

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Users waste time trying to recover from their errors, resulting in productivity loss, reduced satisfaction and accidents. Common system engineering (SE) practices typically disregard system usability. The first part of this article presents real examples of the costs of having the user outside the system boundaries. Recently, researchers have proposed a new framework for complex system engineering (CSE), in which the users are included in the Extended System (ES). CSE considers the users as special cases of cognitive, self-adaptive system elements. With this framework, the human factors (HF) may dominate the system performance and reliability. Current CSE methodology focuses on operability of systems with fuzzy boundaries, and it does not provide the means to solve the exemplified problems of simple, well defined interactive systems. The article presents a methodology for extended system engineering (ESE), a sub discipline of CSE specializing in the features and limitations of the human operators. Typically, usability professionals are concerned about ease of use during the initial stage more than about user errors. The multidisciplinary approach of having a usability expert in the development team falls short of solving the problems, unless the interface of the information flow between the usability experts and the system engineers is well defined. The article presents the principles and means for integrating usability in system engineering, so that user errors are eliminated, and their negative effects are reduced. Part of the principles and means presented here are applicable to the interaction between any elements of any system, regardless of their intelligence.

Service Oriented Architectures (SOA) enable dynamic integration of Web Services (WS) to accomplish a user's need. As such, they are sensitive to user errors. This article presents a framework for mitigating the risks of user errors due to changes in the service delivery context. The underlying methodology incorporates usability in the design, testing, deployment and operation of dynamic collaborative WS, so that the error-prone elements of the User Interface (UI) are identified and eliminated. The methodology incorporates Statistical Process Control (SPC) of Web Service Indices (WSI), obtained by a Decision Support system for User Interface Design (DSUID), in which the users are elements of the control loop.