Visual analytics (VA) systems have been widely used to facilitate
decision-making and analytical reasoning in various application domains. VA
involves visual designs, interaction designs, and data mining, which is a
systematic and complex paradigm. In this work, we focus on the design of
effective visualizations for complex data and analytical tasks, which is a
critical step in designing a VA system. This step is challenging because it
requires extensive knowledge about domain problems and visualization to design
effective encodings. Existing visualization designs published in top venues are
valuable resources to inspire designs for problems with similar data structures
and tasks. However, those designs are hard to understand, parse, and retrieve
due to the lack of specifications. To address this problem, we build KB4VA, a
knowledge base of visualization designs in VA systems with comprehensive labels
about their analytical tasks and visual encodings. Our labeling scheme is
inspired by a workshop study with 12 VA researchers to learn user requirements
in understanding and retrieving professional visualization designs in VA
systems. The theme extends Vega-Lite specifications for describing advanced and
composited visualization designs in a declarative manner, thus facilitating
human understanding and automatic indexing. To demonstrate the usefulness of
our knowledge base, we present a user study about design inspirations for VA
tasks. In summary, our work opens new perspectives for enhancing the
accessibility and reusability of professional visualization designs