"This document describes the Heliophysics Application Programmer’s Interface (HAPI) specification, which is a standard set of services and a standard streaming format for delivering digital time series data"
HAPI is not a set of services, but it is an API specification. Perhaps this is better:
"This document describes the Heliophysics Application Programmer’s Interface (HAPI) specification, which is an API and streaming format specification for delivering digital time series data"
The first sentence is
"This document describes the Heliophysics Application Programmer’s Interface (HAPI) specification, which is a standard set of services and a standard streaming format for delivering digital time series data"
HAPI is not a set of services, but it is an API specification. Perhaps this is better:
"This document describes the Heliophysics Application Programmer’s Interface (HAPI) specification, which is an API and streaming format specification for delivering digital time series data"