One of the central research challenges in the Internet of Things and Ubiquitous Computing domains is how users can be enabled to “program” their personal and industrial smart environments by combining services that are provided by devices around them. We present a service composition system that enables the goal-driven configuration of smart environments for end users by combining semantic metadata and reasoning with a visual modeling tool. In contrast to process-driven approaches where service mashups are statically defined, we make use of embedded semantic API descriptions to dynamically create mashups that fulfill the user’s goal. The main advantage of our system is its high degree of flexibility, as service mashups can adapt to dynamic environments and are fault-tolerant with respect to individual services becoming unavailable. To support users in expressing their goals, we integrated a visual programming tool with our system that allows to model the desired state of a smart environment graphically, thereby hiding the technicalities of the underlying semantics. Possible applications of the presented system include the management of smart homes to increase individual well-being, and reconfigurations of smart environments, for instance in the industrial automation or healthcare domains.

With ever more everyday objects becoming “smart” due to embedded processors and communication capabilities, the provisioning of intuitive user interfaces to control smart things is quickly gaining importance. We present a model-based interface description scheme that enables automatic, modality-independent user interface generation. User interface description languages based on our approach carry enough information to suggest intuitive interfaces while still being easily producible for developers. This is enabled by describing the atomic interactive components of a device and capturing the semantics of interactions with the device. We propose a taxonomy of abstract sensing and actuation primitives and present a smartphone application that can act as a ubiquitous device controller. An evaluation of the mobile application in a laboratory setup, home environments, and an educational setting as well as the results of a user study highlight the accessibility of the proposed scheme for application developers and its suitability for controlling smart devices.

The worldwide adoption of smart meters that measure and communicate residential electricity consumption gives rise to the development of new energy efficiency services. Several particularly promising applications involve the disaggregation of individual appliances within a particular household in terms of their energy demand. In this paper we present an infrastructure and a set of algorithms that make use of smart meters together with smartphones to realize new energy efficiency services (such as itemized electricity bills or targeted energy saving advice). The smartphones, together with a novel filtering approach, much simplify the training process for appliances signature recognition. We also report on the performance of our system that was tested with 8 simultaneous devices, achieving recognition rates of 87%.

We are observing an increasing trend of connecting embedded sensors and sensor networks to the Internet and publishing their output on the Web. We believe that this development is a precursor of a Web of Things, which gives real-world objects and places a Web presence that not only contains a static description of these entities, but also their real-time state. Just as document searches have become one of the most popular services on the Web, we argue that the search for real-world entities (i.e., people, places, and things) will become equally important. However, in contrast to the mostly static documents on the current Web, the state of real-world entities as captured by sensors is highly dynamic. Thus, searching for real-world entities with a certain state is a challenging problem. In this paper, we define the underlying problem, outline the design space of possible solutions, and survey relevant existing approaches by classifying them according to their design space. We also present a case study of a real-world search engine called Dyser designed by the authors.

Reducing their energy consumption has become an important objective for many people. Consumption transparency and timely feedback are essential to support those who want to adjust their behavior in order to conserve energy. In this work, we propose an interactive system that provides instantaneous feedback concerning the energy usage on household and device level. For that, we used and extended the capabilities of a smart electricity meter, built a web-based API to enable interoperability with other applications, and developed a mobile phone interface that allows users to monitor, control, and measure the consumption of single appliances. Our system illustrates a way how usage barriers can be lowered and how high user involvement can be created. By providing users the electricity feedback needed -- in real-time and on device level -- the system allows for identifying the biggest energy guzzlers and helps users decrease their energy consumption.

We present our results in the conceptual design and the implementation of ubiquitous computing applications using smart identification technologies. First, we describe such technologies and their potential application areas, followed by an overview of some applications we have developed. Based on the experiences we gained from the development of these systems, we point out design concepts that we find useful for structuring and implementing such applications. Building upon these concepts, we have created two frameworks based on Jini (i.e., distributed Java objects) and Web services to support the development of ubiquitous computing applications that make use of smart identification technology. We describe our prototype frameworks, discuss the underlying concepts and present some lessons learned.

It is shown that the termination detection problem for distributed computations can be modeled as an instance of the garbage collection problem. Consequently, algorithms for the termination detection problem are obtained by applying transformations to garbage collection algorithms. The transformation can be applied to collectors of the “mark-and-sweep” type as well as to reference-counting protocol of Lermen and Maurer, the weighted-reference-counting protocol, the local-reference-counting protocol, and Ben-Ari's mark-and-sweep collector into termination detection algorithms. Known termination detection algorithms as well as new variants are obtained.

Several variants of the simple Chang-Roberts algorithm are simulated. The empirical analysis shows that the algorithms compare very favorably to other ring-based election algorithms. For various ring sizes and numbers of concurrent starters the average message complexity, its distribution, and its standard deviation were studied. Simulation results show that the algorithm is far better than the rather conservative mathematical estimations indicate.>

This paper gives an overview of the INCAS (INCremental Architecture for distributed Systems) multicomputer project, which aims at the development of a comprehensive methodology for the design and implementation of locally distributed systems. A structuring concept for distributed operating systems has been developed and integrated into the system implementation language LADY. The concurrent high-level programming language CSSA, based on the actor model, has been designed for the implementation of distributed applications. A substantial effort in the INCAS project is directed towards the development of a distributed test methodology. An experimental system has been implemented on a network of ten MC68000 microcomputers. Preliminary experience with the methodology has been gained from a small number of prototype applications.

Abstract An efficient and systematic LL(1) error recovery method is presented that has been implemented for an LL(1) parser generator. Error messages which provide good diagnostic information are generated automatically. Error correction is done by discarding some input symbols and popping up some symbols from the parsing‐stack in order to restore the parser to a valid configuration. Thus, symbol deletions and insertions are simulated. The choice between different possible corrections is made by comparing the cost of the inserted (popped) symbols with the reliability value of the recovery symbol (the first input symbol that is not discarded). Our concept of reliability is based on the observation that input symbols differ from each other in their ability to serve as recovery points. A high reliability value of a symbol asserts that it was probably not placed in the input by accident. So it is reasonable not to discard that symbol but to resume parsing. This is done even if a string with high insert‐cost has to be inserted before that symbol in order to fit it to the part of the program that has already been analysed. The error recovery routine is invoked only when an error is detected. Thus, there is no additional time required for parsing correct programs. Error‐correcting parsers for different languages, including Pascal, have been generated. Some experimental results are summarized.