Introduction to the Special Issue: SORT 2010

The increasing complexity of contemporary embedded computing systems requires the use of selfmanagement in order to handle unforeseen changes in both hardware and application environments (i.e., hardware/software defects, resource changes, and non-continual feature usage). Moreover, often these systems are distributed, running on processor architectures with multiple cores, which may require self-organization to ensure efficiency and reliability. Real-time properties are another key issue in many complex systems. Adaptive and self-organized properties extend the area of operations and improve the efficiency of the system resources at the cost to introduce additional complexity, overhead, and resource requirements. Consequently, real-time adaptive systems must be carefully analyzed, designed, and built, taking into account the right tradeoffs between flexibility and complexity while accomplishing time-constrains. The combination of the flexibility and ‘uncertain behavior’ of self-organizing systems with timepredictability is a grand challenge. Therefore, substantial research has been done in the last years to address the so-called Self-X features (e.g., self-configuration, self-optimization, self-adaptation, self-healing, and self-protection). The Workshop on Self-Organizing Real-Time Systems (SORT) is specifically dedicated to research on adaptive real-time systems. SORT started in 2010 as a workshop attached at International Symposium on Object/Component/Service-Oriented Real-Time Distributed Computing, organized in Sevilla (Spain). The purpose of this workshop is to provide an open forum to discuss new and ongoing research that is centered on the idea of adaptability in real-time systems. The target audience includes researchers from academia, tool vendors, system suppliers, and users in industry who are interested in all aspects of the topics mentioned in the succeeding text. This special issue of Concurrency and Computation: Practice and Experience contains five invited papers from the SORT 2010 workshop that has been expanded and carefully peer reviewed. The first paper, titled Realizing Real-time Centroid Detection of Multiple Objects with Marching Pixels Algorithms on Customizing Hardware [1], describes a class of emergent algorithms, called Marching Pixels, based on hardware agents that can be used in smart camera chips. These algorithms are virtually crawling in a pixel grid image to find attributes of an arbitrary number of objects given in an image (e.g., centroid, rotation, and size), which replay times can be determined. This work also presents an example and its corresponding architecture. The parallel architecture contains a specific instruction set allowing the execution of these specific algorithms and also arbitrary Cellular Automata algorithms. The obtained results using Field Programmable Gate Array (FPGA) and Application-Specific Integrated Circuit (ASIC) are compared with the solution addressed on a real hardware architecture. A challenge in the development of adaptive systems is how to provide adaptability to the application, because this process affects all phases of the application live-cycle (e.g., methodologies, modeling, analysis, testing, and implementation). In the paper A Methodology for Real-Time Self-Organized Autonomous Clustering in Mobile Ad Hoc Networks [2], Yoshiaki Kakuda et al. develop autonomous clustering with high scalability and adaptability. In this autonomous clustering, interval and power for transmitting messages are dynamically changed depending on clusters mobility and density variations. Because mobility and density can be estimated by local information, the clusters are self-organized in a real-time way. Self-management systems are based on concepts and aspects related to both artificial intelligence and awareness. Here, the biggest challenge is still how to properly develop and verify such systems. In the paper The ASSL Approach to Specifying Self-Managing Embedded Systems [3], Emil Vassev and Mike Hinchey present a formal approach to specifying embedded systems capable