With the advent of the internet of things and industry 4.0 an enormous amount of data is produced at the edge of the network. Due to a lack of computing power, this data is currently send to the cloud where centralized machine learning models are trained to derive higher level knowledge. With the recent development of specialized machine learning hardware for mobile devices, a new era of distributed learning is about to begin that raises a new research question: How can we search in distributed machine learning models? Machine learning at the edge of the network has many benefits, such as low-latency inference and increased privacy. Such distributed machine learning models can also learn personalized for a human user, a specific context, or application scenario. As training data stays on the devices, control over possibly sensitive data is preserved as it is not shared with a third party. This new form of distributed learning leads to the partitioning of knowledge between many devices which makes access difficult. In this paper we tackle the problem of finding specific knowledge by forwarding a search request (query) to a device that can answer it best. To that end, we use a entropy based quality metric that takes the context of a query and the learning quality of a device into account. We show that our forwarding strategy can achieve over 95 accuracy in a urban mobility scenario where we use data from 30 000 people commuting in the city of Trento, Italy.
By 2020, the Internet of Things will consist of 26 Billion connected devices. All these devices will be collecting an innumerable amount of raw observations, for example, GPS positions or communication patterns. In order to benefit from this enormous amount of information, machine learning algorithms are used to derive knowledge from the gathered observations. This benefit can be increased further, if the devices are enabled to collaborate by sharing gathered knowledge. In a massively distributed environment, this is not an easy task, as the knowledge on each device can be very heterogeneous and based on a different amount of observations in diverse contexts. In this paper, we propose two strategies to route a query for specific knowledge to a device that can answer it with high confidence. To that end, we developed a confidence metric that takes the number and variance of the observations of a device into account. Our routing strategies are based on local routing tables that can either be learned from previous queries over time or actively maintained by interchanging knowledge models. We evaluated both routing strategies on real world and synthetic data. Our evaluations show that the knowledge retrieved by the presented approaches is up to @math as accurate as the global optimum.