When the orders were added, there was a modification to the FIX specification for the exchange. For example: http://www.directedge.com/Portals/0/docs/Direct%20E

When the orders were added, there was a modification to the FIX specification for the exchange. For example: http://www.directedge.com/Portals/0/docs/Direct%20Edge%20Next%20Gen%20FIX%20Manual.pdf http://www.directedge.com/Portals/0/docs/Direct%20Edge%20Nex.... It is everyone who trades on that exchange's responsibility to stay up to date with what's available, and how it interacts with their trading strategy. "concealed", in this context, just means "too lazy to carefully read the documentation".