Diva: A Declarative and Reactive Language for In-Situ Visualization.

The use of adaptive workflow management for in situ visualization and analysis has been a growing trend in large-scale scientific simulations. However, coordinating adaptive workflows with traditional procedural programming languages can be difficult, because system flow is determined by unpredictable scientific phenomena, which often appear in an unknown order and can evade event handling. This makes the implementation of adaptive workflows tedious and errorprone. Recently, reactive and declarative programming paradigms have been recognized as well-suited solutions to similar problems in other domains. Not much work has been done to adopt these methods into the field of in situ visualization and analysis. With this paper, we present a proof-of-concept language, parser and runtime system for designing adaptive systems through a declarative and reactive programming paradigm. We illustrate how an adaptive workflow system is implemented using our approach, and demonstrate it with use cases from real scientific simulations.