Henrik Bærbak Christensen

Pervasive Computing Support for Hospitals: An overview of the Activity-Based Computing Project

The activity-based computing project researched pervasive computing support for clinical hospital work. Such technologies have potential for supporting the mobile, collaborative, and disruptive use of heterogeneous embedded devices in a hospital

Supporting Human Activities - Exploring Activity-Centered Computing

In this paper we explore an activity-centered computing paradigm that is aimed at supporting work processes that are radically different from the ones known from office work. Our main inspiration is healthcare work that is characterized by an extreme degree of mobility, many interruptions, ad-hoc collaboration based on shared material, and organized in terms of well-defined, recurring, work activities. We propose that this kind of work can be supported by a pervasive computing infrastructure together with domain-specific services, both designed from a perspective where work activities are first class objects. We also present an exploratory prototype design and first implementation and present some initial results from evaluations in a healthcare environment.

Application requirements for middleware for mobile and pervasive systems

In this paper, we examine the requirements for future middleware to support mobile and pervasive applications and identify key research areas. We illustrate the research areas with requirements identified in two specific research projects concerning pervasive healthcare and home entertainment.

The Unified Extensional Versioning Model

Versioning of components in a system is a well-researched field where various adequate techniques have already been established. In this paper, we look at how versioning can be extended to cover also the structural aspects of a system. There exist two basic techniques for versioning - intentional and extensional - and we propose a unified extensional versioning model for versioning of both components and structure in the same way. The unified model is described in detail and three different policies that can be implemented on top of the general model are exemplified/illustrated by three prototype tools constructed by the authors. The model is analysed with respect to the number of versions and configurations it generates and has to manage. Finally, the unified extensional model is compared to more traditional intentional models on some important parameters. The conclusions are that the unified model is indeed viable. It not only provides the functionality offered by the intentional model with respect to flexibility during development and management of combinatoric complexity, but also offers a framework for management of configurations that enables systems to provide much more advanced support than is commonly available.

Using Logic Programming to Detect Activities in Pervasive Healthcare

In this experience paper we present a case study in using logic programming in a pervasive computing project in the healthcare domain. An expert system is used to detect healthcare activities in a pervasive hospital environment where positions of people and things are tracked. Based on detected activities an activity-driven computing infrastructure provides computational assistance to healthcare staff on mobile-and pervasive computing equipment. Assistance range from simple activities like fast log-in into the electronic patient medical record system to complexact ivities like signing for medicine given to specific patients. We describe the role of logic programming in the infrastructure and discuss the benefits and problems of using logic programming in a pervasive context.

Analysis and design of software ecosystem architectures – Towards the 4S telemedicine ecosystem

Abstract Context Telemedicine, the provision of health care at a distance, is arguably an effective way of increasing access to, reducing cost of, and improving quality of care. However, the deployment of telemedicine is faced with standards that are hard to use, application-specific data models, and application stove-pipes that inhibit the adoption of telemedical solutions. To which extent can a software ecosystem approach to telemedicine alleviate this? Objective In this article, we define the concept of software ecosystem architecture as the structure(s) of a software ecosystem comprising elements, relations among them, and properties of both. Our objective is to show how this concept can be used (i) in the analysis of existing software ecosystems and (ii) in the design of new software ecosystems. Method We performed a mixed-method study that consisted of a case study and an experiment. For (i), we performed a descriptive, revelatory case study of the Danish telemedicine ecosystem and for (ii), we experimentally designed, implemented, and evaluated the architecture of 4S. Results We contribute in three areas. First, we define the software ecosystem architecture concept that captures organization, business, and software aspects of software ecosystems. Secondly, we apply this concept in our case study and demonstrate that it is a viable concept for software ecosystem analysis. Finally, based on our experiments, we discuss the practice of software engineering for software ecosystems drawn from experience in creating and evolving the 4S telemedicine ecosystem. Conclusion The concept of software ecosystem architecture can be used analytically and constructively in respectively the analysis and design of software ecosystems.

Here, there and everywhere - on the recurring use of turtle graphics in CS1

The Logo programming language implements a virtual drawing machine—the turtle machine. The turtle machine is well-known for giving students an intuitive understanding of fundamental procedural programming principles. In this paper we present our experiences with resurrecting the Logo turtle in a new object-oriented way and using it in an introductory object-oriented programming course. While, at the outset, we wanted to achieve the same qualities as the original turtle (understanding of state, control flow, instructions) we realized that the concept of turtles is well suited for teaching a whole range of fundamental principles. We have successfully used turtles to give students an intuitive understanding of central object-oriented concepts and principles such as object, class, message passing, behaviour, object identification, subclasses and inheritance; an intuitive understanding of recursion; and to show students the use of abstraction in practice as the turtles at a late stage in the course becomes a handy graphics library used in a context otherwise unrelated to the turtles.

Exploring quality attributes using architectural prototyping

A central tenet of software architecture design is to base this on a formulation of desired quality attributes, such as buildability, performance, and availability of the target system. Thus there is a need for architectural evaluation—ensuring the architecture’s support for desired quality attributes—and a variety of evaluation techniques have been developed, described, and used. Architectural prototyping is an experimental approach that creates executable ‘skeleton’ systems to investigate architectural qualities of a future system. Architectural prototyping is a learning vehicle for exploring an architectural design space as well as an evaluation technique. The contribution of this paper is to explore the evaluation aspect of architectural prototypes from an analytical standpoint. We present an analysis and discussion of architectural prototyping in the context of two well-established quality frameworks. Our analysis concludes that architectural prototyping is a viable evaluation technique that may evaluate architectural quality attributes and especially valuable in cases where the balance between opposing qualities must be assessed.

Evaluating OO example programs for CS1

Example programs play an important role in learning to program. They work as templates, guidelines, and inspiration for learners when developing their own programs. It is therefore important to provide learners with high quality examples. In this paper, we discuss properties of example programs that might affect the teaching and learning of object-oriented programming. Furthermore, we present an evaluation instrument for example programs and report on initial experiences of its application to a selection of examples from popular introductory programming textbooks.

Frameworks: putting design patterns into perspective

Design patterns have made a strong impact on how object-oriented software is designed, implemented, and communicated in industrial projects. Teaching patterns is therefore of great importance. Patterns, however, have a natural catalogue-like nature, that easily misleads us into to lecturing them one at a time. This leaves an impression of patterns as isolated solutions to independent problems. We present our experience with trying to counteract this problem by using a well-engineered framework, JHotDraw, as a case study in how patterns work together to define a flexible and compositional software system of high quality.