A Grass-roots Standard for Time Series Data in any Domain: HAPI
J. D. Vandegriff, Robert S. Weigel, Jeremy B. Faden, Alex Antunes · 2025
We describe a simple interface for accessing time series numeric data: the Heliophysics Application Programmer's Interface (HAPI). Although it started in NASA's Heliophysics domain, no Heliophysics idioms are present in the standard, and HAPI can be used to serve any tabular, numeric data that is indexed by time. HAPI was the result of a community push to standardize similar access methods at multiple data centers, and it is now in use at 12 data centers around the world, with over 12,000 datasets available in a standard way. HAPI offers a more conceptual view of the data, independent of the storage arrangements at a server. It also is not intended to replace an existing server's API, but to sit alongside that API. The project is mature, with a reference server available, as well as clients in multiple programming languages. We will present an overview of the API and compliance with FAIR principles. We also will describe some of the visualization and analysis tools being developed now that standardized access is becoming a reality. We invite discussion with other time series data providers in other domains.