IImfChannelList.h:
// Support for image layers:
//
// In an image file with many channels it is sometimes useful to
// group the channels into "layers", that is, into sets of channels
// that logically belong together. Grouping channels into layers
// is done using a naming convention: channel C in layer L is
// called "L.C".
//
// For example, a computer graphic image may contain separate
// R, G and B channels for light that originated at each of
// several different virtual light sources. The channels in
// this image might be called "light1.R", "light1.G", "light1.B",
// "light2.R", "light2.G", "light2.B", etc.
//
// Note that this naming convention allows layers to be nested;
// for example, "light1.specular.R" identifies the "R" channel
// in the "specular" sub-layer of layer "light1".
//
// Channel names that don't contain a "." or that contain a
// "." only at the beginning or at the end are not considered
// to be part of any layer.