This directory contains subdirectories for two different revisions of the PEX and PEXlib specifications. PEX5.1 contains the PEX and PEXlib version 5.1 specifications, which are official X Consortium Standards. PEX5.2 contains the PEX and PEXlib version 5.2 specifications, which are Draft Consortium Standards. The Draft Consortium Standards are considered to be viable and complete specifications. However, they are not official X Consortium standards because the proof of concept implementation requirement has not yet been fulfilled. The PEX 5.2 specifications will remain in Draft Consortium Standard status until the proof of concept criteria have been met.