Supporting Tele-Teaching: visualization aspects

A strong trend towards use of collaborative systems in teaching can be observed. Often first experience is gained by conducting seminars or lectures with existing tools, e.g. using the MBone. These tests generally find that the support of existing, mainly generic tools is not adequate for Tele-teaching. While some projects address learning aspects directly, these tend to be limited in scalability, mainly addressing smaller groups. Our approach is to develop a general framework (MACS: Modular Advanced Collaboration System) and basic components which can be used in a variety of scenarios. Currently the two main scenarios supported are a discussion group consisting of few (about 10) participants with equal rights, and a lecture scenario with more participants (up to 100) and a lecturer in control. For these scenarios, not only aspects of session control are relevant, but methods as well to provide feedback to the lecturer about the current session. This is achieved through a combination of visualization methods customized for the selected scenario. The session control uses a graphical representation of a room typically used in the specified scenario in order to provide feedback and to allow ease of use. The control marks tools currently in use allowing the lecturer and students to easily identify and participate in the corresponding media representation (e.g. audio and video). A special feedback tool allows rating, and can be used to gain feedback from the students about the received video and audio quality, the speed of presentation or any other resource one wants a rating on. These visualization measures combined with the floor control provided by MACS allow to conduct a lecture in an efficient manner.     

情形实例驱动的软件需求模型自动生成

通过对使用情形的分析来进行需求获取和需求分析可以使软件需求分析的工作较为系统和有序。由于每一个情形实例都只从特定的使用者的角度，根据所需达到的特定使用目的，针对特定的使用条件，来描述一个复杂系统中的一个局部，与对整个复杂系统的需求进行分析和描述相比，在特定情形实例下对软件需求进行分析与描述较简单。然而，如何保证情形实例描述之间的一致性，如何从情形实例的描述获得整个软件系统的需求定义则是以情形实例分     

A method and tools for large scale scenarios

Formal scenarios have many uses in requirements engineering, validation, performance modeling, and test generation. Many tools and methodologies can handle scenarios when the number of steps (interleaved inputs and outputs of the target system) is reasonably small. However, scenario based techniques do not scale well with the number of steps, number of actors, and complexity of behaviors and system interactions to be specified in the scenario. First, it is impractically tedious and error-prone to specify thousands of input steps and corresponding expected outputs. Second, even if one can write down such large scale scenarios, confidence in their correctness is naturally low. Third, complex systems requiring large scale scenarios tend to require many such scenarios to adequately cover the behavior space. This paper describes the motivations for and problems of large scale scenarios, as well as the LSS method, which uses automated and semi-automated techniques in describing, maintaining, communicating, and using large scale scenarios in requirements engineering. The method is illustrated in two widely divergent application domains: military live training instrumentation and electronic mail servers. A case study demonstrates the practical and beneficial use of LSS in architectural modeling of a complex, real-world system design. A two page extended abstract of this paper appeared in Proc. 21st ACM/IEEE Intl. Conf. on Software Engineering (ASE 2006).     

Guiding goal modeling using scenarios

Even though goal modeling is an effective approach to requirements engineering, it is known to present a number of difficulties in practice. The paper discusses these difficulties and proposes to couple goal modeling and scenario authoring to overcome them. Whereas existing techniques use scenarios to concretize goals, we use them to discover goals. Our proposal is to define enactable rules which form the basis of a software environment called L'Ecritoire to guide the requirements elicitation process through interleaved goal modeling and scenario authoring. The focus of the paper is on the discovery of goals from scenarios. The discovery process is centered around the notion of a requirement chunk (RC) which is a pair 〈Goal, Scenario〉. The paper presents the notion of RC, the rules to support the discovery of RCs and illustrates the application of the approach within L'Ecritoire using the ATM example. It also evaluates the potential practical benefits expected from the use of the approach     

Automating test generation for discrete event oriented embedded systems

A method for the automatic generation of test scenarios from the behavioral requirements of a system is presented in this paper. The generated suite of test scenarios validates the system design or implementation against the requirements. The approach proposed here uses a requirements model and a set of four algorithms. The requirements model is an executable model of the proposed system defined in a deterministic state-based modeling formalism. Each action in the requirements model that changes the state of the model is identified with a unique requirement identifier. The scenario generation algorithms perform controlled simulations of the requirements model in order to generate a suite of test scenarios applicable for black box testing. Measurements of several metrics on the scenario generation algorithms have been collected using prototype tools.     

A formal approach to scenario integration

The scenario technique is an interesting approach for eliciting requirements. A formal approach to scenario generation has made it even more attractive. The next logical step is to integrate several scenarios into one single, consistent, specification. In this work, a mixed approach, involving formal and informal steps is proposed for performing this task. The system's formal specification is expressed as a finite state machine. The specifications of two interacting scenarios are integrated in a procedure involving formal and informal steps. Then several algorithms based on the properties of the model, are applied to detect three classes of errors: mistakes made by the analyst during the informal steps of the integration, inconsistencies between the scenarios, and incompleteness of both scenarios. Each algorithm detects the corresponding specification errors and in addition, suggests the corrections to apply. The formal techniques applied in this work could be the basis of a CASE tool for scenario‐based requirements engineering.     

Discovering and Managing Access to Private Services in Collaborative Sessions

An approach that integrates service discovery with the Internet Engineering Task Force session initiation protocol to support service discovery of private services across a collaborative session is presented. Embedding the service discovery protocol within a session protocol facilitates the discovery of private services in a safe and controlled manner. Access to services is managed by defining local scopes that are shared among participants in the collaborative session. The fundamentals of the approach are presented using a simple two-party scenario and further extended by describing the approach using both central and peer-to-peer collaborative scenarios. Finally, the feasibility of the approach is demonstrated through a proof-of-concept demonstration of the sharing of Bluetooth services located in a private wireless personal area network across a telephone conversation     

Modeling urban development and its exposure to river flood risk in Southeast Asia

Countries in Southeast Asia have been developing quickly from a predominantly rural to predominantly urban society, leading to a rapid increase in urban land. This increase in urban land has mainly occurred in river deltas and floodplains, exposing humans and human assets to flood hazard. Here we present an assessment of current and future flood risk in five countries of mainland Southeast Asia, using a new modeling approach that accounts for differences in urban land systems. To that effect we mapped urban land on a rural-urban gradient and projected urban development until the year 2040 in two contrasting scenarios. The urban expansion scenario mainly projects the development of new urban areas, while the intensification emphasizes an increase in the number of inhabitants in already existing urban areas. Subsequently, we assessed the expected annual damage due to flood risk, using country specific exposure values for different land-system classes along the rural-urban gradient, based on typical construction materials. Results indicate that expected annual flood damage will increase in all countries and in both scenarios, ranging from +8% in Thailand to +211% in Laos. We showed that preferable development pathways are context dependent. In Cambodia and Laos, the increase in flood risk was largest for the intensification scenario, while for Myanmar, Thailand and Vietnam, the increase in flood risk was largest in the urban expansion scenario.     

Scenario advisor tool for requirements engineering

This study investigates the usefulness of a scenario advisor tool which was built to help requirements engineers to generate sufficient sets of scenarios in the domain of socio-technical systems. The tool provides traceability between scenario models and requirements and helps to generate new scenarios and scenario variations. Through two series of evaluation sessions, we found that the scenario advisor tool helped users to write more sound scenarios without any domain knowledge, and to generate more variations on existing scenarios by providing specific scenario-generation hints for each scenario component. The tool should improve the reliability of requirements elicitation and validation.     

Scenario Analysis in an Automated Tool for Requirements Engineering

 This paper presents an automated tool for scenario-driven requirements engineering where scenario analysis plays the central role. It is shown that a scenario can be described by three views of data flow, entity relationship and state transition models by slight extensions of classic data flow, entity relationship and state transition diagrams. The notions of consistency and completeness of a set of scenarios are formally defined in graph theory terminology and automatically checked by the tool. The tool supports automatic validation of requirements definitions by analysing the consistency between a set of scenarios and requirements models. It also supports automatic synthesis of requirements models from a set of scenarios. Its utility and usefulness are demonstrated by a non-trivial example in the paper. Case studies of the tools are also presented.     

Deriving Goals from a Use-Case Based Requirements Specification

Use cases and scenarios have emerged as prominent analysis tools during requirements engineering activities due to both their richness and informality. In some instances, for example when a project’s budget or schedule time is reduced at short notice, practitioners have been known to adopt a collection of use cases as a suitable substitute for a requirements specification. Given the challenges inherent in managing large collections of scenarios, this shortcut is cause for concern and deserves focused attention. We describe our experiences during a goal-driven requirements analysis effort for an electronic commerce application. In particular, we identify the specific risks incurred, focusing more on the challenges imposed due to traceability, inconsistent use of terminology, incompleteness and consistency, rather than on traditional software project management risks. We conclude by discussing the impact of the lessons learned for requirements engineering in the context of building quality systems during goal and scenario analysis.     

Scenario construction and reduction applied to stochastic power generation expansion planning

A challenging aspect of applying stochastic programming in a dynamic setting is to construct a set of discrete scenarios that well represents multivariate stochastic processes for uncertain parameters. Often this is done by generating a scenario tree using a statistical procedure and then reducing its size while maintaining its statistical properties. In this paper, we test a new scenario reduction heuristic in the context of long-term power generation expansion planning. We generate two different sets of scenarios for future electricity demands and fuel prices by statistical extrapolation of long-term historical trends. The cardinality of the first set is controlled by employing increasing length time periods in a tree structure while that of the second set is limited by its lattice structure with periods of equal length. Nevertheless, some method of scenario thinning is necessary to achieve manageable solution times. To mitigate the computational complexity of the widely-used forward selection heuristic for scenario reduction, we customize a new heuristic scenario reduction method named forward selection in wait-and-see clusters (FSWC) for this application. In this method, we first cluster the scenarios based on their wait-and-see solutions and then apply fast forward selection within clusters. Numerical results for a twenty year generation expansion planning case study indicate substantial computational savings to achieve similar solutions as those obtained by forward selection alone.     

The diversity of socio-economic pathways and CO2 emissions scenarios: Insights from the investigation of a scenarios database

The new scenario framework developed by the climate change research community rests on the fundamental logic that a diversity of socio-economic pathways can lead to the same radiative forcing, and therefore that a given level of radiative forcing can have very different socio-economic impacts. We propose a methodology that implements a “scenario discovery” cluster analysis and systematically identifies diverse groups of scenarios that share common outcomes among a database of socio-economic scenarios. We demonstrate the methodology with two examples using the Shared Socio-economic Pathways framework. We find that high emissions scenarios can be associated with either high or low per capita GDP growth, and that high productivity growth and catch-up are not necessarily associated with high per capita GDP and high emissions.     

Requirements development in scenario-based design

We describe and analyze the process of requirements development in scenario based design through consideration of a case study. In our project, a group of teachers and system developers initially set out to create a virtual physics laboratory. Our design work centered on the collaborative development of a series of scenarios describing current and future classroom activities. We observed classroom scenarios to assess needs and opportunities, and envisioned future scenarios to specify and analyze possible design moves. We employed claims analysis to evaluate design trade-offs implicit in these scenarios, to codify the specific advantages and disadvantages in achieving requirements. Through the course of this process, the nature of our project requirements has evolved, providing more information but also more kinds of information. We discuss the utility of managing requirements development through an evolving set of scenarios, and the generality of the scenario stages from this case study     

Representing older people: towards meaningful images of the user in design scenarios

Designing for older people requires the consideration of a range of design problems, which may be related to difficult and sometimes highly personal matters. Issues such as fear, loneliness, dependency, and physical decline may be hard to observe or discuss in interviews. Pastiche scenarios and pastiche personae are techniques that employ characters to create a space for the discussion of new technological developments and user experience. This paper argues that the use of fictional characters can help to overcome restrictive notions of older people by disrupting designers’ prior assumptions. In this paper, we reflect on our experiences using pastiche techniques in two separate technology design projects that sought to address the needs of older people. In the first pastiche scenarios were developed by the designers of the system and used as discussion documents with users. In the second pastiche personae were used by groups of users themselves to generate scenarios which were scribed for later use by the design team. We explore how the use of fictional characters and settings can generate new ideas and undercut the potential in scenarios, for weak characterisation of “the user” to permit scenario writers to fit characters to technology rather than vice versa. To assist in future development of pastiche techniques in designing for older people, we provide an array of fictional older characters drawn from literary and popular culture.     

Rich-media scenarios for discovering requirements

Walking through scenarios is an effective technique for discovering requirements, but scenarios can differ widely in their abstraction levels and representation forms. Some requirements analysts use scenarios that describe a system's external visible behavior. Others use live sequence charts to model a system's dynamic behavior. Requirements analysts also use scenarios for everything from explaining a current system to walking through a future system's behavior to discover its requirements. However, determining the right form of scenarios for different requirements tasks remains an open question -one we're investigating with ART-SCENE. ART-SCENE is an Internet-based environment for generating and walking through text scenarios. The ART-SCENE tool supports rich media scenarios in requirement discovery. These scenarios help stakeholders recognize events that a system will have to handle.     

Modular framework support for context-aware mobile cinema

In this paper we describe a novel approach for interactive cinema based on context-aware narration using handheld computers. The paper describes both the artistic approach and the ubiquitous computing framework developed to realize the scenario. This framework has been used in various projects, including the described video production course at the ISNM, where five interactive cinema concepts have been developed and shown during a public demonstration. In our approach, a new type of user experience has been established by placing the viewer inside the movie’s physical locations during playback. Moreover, the developed ubiquitous computing framework provides a foundation for future work in the area of ad-hoc, service-oriented Ubicomp scenarios.