This document defines a coverage processing language for server-side extraction, filtering, processing, analytics, and fusion of multi-dimensional geospatial coverages representing, for example, spatiotemporal sensor, image, simulation, or statistics datacubes. Services implementing this language provide access to original or derived sets of coverage information, in forms that are useful for client-side consumption. ISO 19123-3 relies on the abstract coverage model defined in ISO 19123-1. In this document, regular and irregular multi-dimensional grids are supported, for axis that may carry spatial, temporal, or any other semantics. Future versions may additionally support further axis types as well as point clouds and meshes. The language is functionally defined and free of any side effects has a solid conceptual foundation; only two constructs establish all coverage processing: A coverage constructor builds a coverage, either from scratch or by deriving it from one or more other coverages. The ISO 19123-3 language is independent from any particular request and response encoding, as no concrete request/response protocol is assumed. Hence, this standard does not define a service, but acts as the foundation for defining service standards functionality. One such target framework is OGC Web Coverage Service (WCS)[3]. In its current version ISO 19123-3 supports ISO 19123-1 grid coverages with index, regular, and irregular axes. In the future it is foreseen that the standard gets extended so as to address all coverage types of ISO 19123-1.