Adobe has thus far released two CID-keyed OpenType/CFF fonts that use the special-purpose Adobe-Identity-0 ROS (“ROS” is an abbreviation for /Registry, /Ordering, and /Supplement, which represent the three /CIDSystemInfo dictionary elements that are present in CIDFont and CMap resources): Kazuraki SP2N L (かづらき SP2N L) and Kenten Generic. The former is a commercial OpenType/CFF font, and the latter is an open source one. I have also developed several Adobe-Identity-0 ROS OpenType/CFF fonts for testing purposes, many of which have been provided in recent CJK Type Blog articles, the most recent of which being the May 9th, 2012 article.
The big question that may be on a font developer’s mind is under what circumstances is it appropriate to use the Adobe-Identity-0 ROS?
The answer is surprisingly simple:
If the glyphs correspond to one of the public ROSes—Adobe-CNS1-6, Adobe-GB1-5, Adobe-Japan1-6, or Adobe-Korea1-2—or a subset thereof, then using a public ROS is recommended. It is never a problem to build fonts that include only a subset of the glyphs in a public ROS.
Otherwise, the Adobe-Identity-0 ROS is a better choice.
One advantage of using a public ROS is that existing resources can be leveraged, such as CMap resources, GSUB feature definitions, and so on. When using the Adobe-Identity-0 ROS, these resources must be created. The March 7, 2012 CJK Type Blog article details how to build UTF-32 CMap resources, including an example for the Adobe-Identity-0 ROS.