## Changes Introduced in V4.0

The following describes the most significant changes which occurred in the AST library between versions V3.7 and V4.0:

1. Experimental support for reading IVOA Space-Time-Coordinates (STC-X) descriptions using the XmlChanXmlChan class has been added. Support is included for a subset of V1.20 of the draft STC specification.

2. A new set of methods (AST_REBIN<X>/astRebin<X>) has been added to the MappingMapping class. These are flux-conserving alternatives to the existing AST_RESAMPLE<X>/astResample<X> methods.