Automatic event-based synchronization of multimodal data streams from wearable and ambient sensors

A major challenge in using multi-modal, distributed sensor systems for activity recognition is to maintain a temporal synchronization between individually recorded data streams. A common approach is to use well defined ‘synchronization actions’ performed by the user to generate, easily identifiable pattern events in all recorded data streams. The events are then used to manually align data streams. This paper proposes an automatic method for this synchronization. We demonstrate that synchronization actions can be automatically identified and used for stream synchronization across widely different sensors such as acceleration, sound, force, and a motion tracking system. We describe fundamental properties and bounds of our event-based synchronization approach. In particular, we show that the event timing relation is transitive for sensor groups with shared members. We analyzed our synchronization approach in three studies. For a large dataset of 5 users and totally 308 data stream minutes we achieved a synchronization error of 0.3 s for more than 80% of the stream

A communication library to support concurrent programming courses

A number of communication libraries have been written to support concurrent programming. For a variety of reasons, these libraries generally are not well-suited for use in undergraduate courses. We have written a communication library uniquely tailored to an academic environment. The library provides two levels of communication abstraction (topology and channel) and supports communication among threads, processes on the same machine, and processes on different machines, via a unified interface. The routines facilitate controlled message loss along channels and can be integrated with an existing graphical tool that supports visualization of the communication that occurs. An editor has been developed for automatic code generation for arbitrary topologies via a graphical interface. All these tools run over Solaris, Linux, and Windows

Consistency and Availability in Microservice Architectures

For the most part, the first instances of microservice architectures have been deployed for the benefit of the so-called Internet-scale companies in contexts where availability is a critical concern. Their success in this context, along with their promise to be more agile than competing solutions in adapting to changing needs, soon attracted the interest of very diverse classes of business domains characterized by different priorities with respect to non-functional requirements. Microservices embraced this challenge, showing a unique ability to allow for a plethora of solutions, enabling developers to reach the trade-off between consistency and availability that better suits their needs. From a design point of view this translates into a vast solution space. While this can be perceived as an opportunity to enjoy greater freedom with respect to other architectural styles it also means that finding the best solution for the problem at hand can be complex and it is easier to incur in errors that can put a whole project at risk. In this paper we review some possible solutions to address common problems that arise when adopting microservices and we present strategies to address consistency and availability; we also discuss the impact these strategies have on the design space