**Preface to "Advanced Process Monitoring for Industry 4.0"**

Since the seminal work of W.A. Shewhart in the mid 1920s, initiated at Western Electric Company and continued afterwards at Bell Labs, process monitoring (PM) has become a cornerstone of modern industry, embodying a coherent and systematic methodology to continuously assess process stability and diagnose the origin of faults and process upsets. Having emerged during the 2nd industrial revolution, PM greatly expanded during the 3rd technological wave, evolving and adapting its body of knowledge to fulfill the same fundamental goals in increasingly diverse and challenging scenarios. Its wide success has significantly contributed to pushing forward the performance and effectiveness of plant operations, positively impacting process efficiency, safety, the environment, and the companies' bottom line results. Today, we are witnessing the dawn of a new industrial revolution, already coined as Industry 4.0. Again, as before, new challenges arise that need to be handled in order to perform PM in more complex multiscale processes, through the analysis of "extreme data" (in terms of volume, velocity, variety, quality, etc.), in real time. In this Special Issue, a collection of 12 contributions provide an updated overview of the challenges that PM is currently facing and how they can be effectively addressed. Real case studies are cited and new solutions proposed and discussed. We sincerely hope these works catalyze the efforts of the research community and inspire more teams to join in and embrace the many PM challenges lying ahead.

> **Marco S. Reis, Furong Gao** *Editors*
