inability to describe sets of limits (alarms) and conversions (polynomials) and then select a set per parameter depending on mission phase (JWST)

JWST hold conversion and limits in a seperate file that are grouped. Certains "sets" can be used for different mission phases such as test, on-orbit and so on, or for any reason deemed appropriate. XTCE allows one to specify at MOST one of each of these per parameterType

MER supports a Union construct because their abstract data types live past decomm. ASIST also supports the same idea – that an abstract data type onboard the spacecraft MAY live past decomm. Although it is possible to let multiple parameters overlap, in a sense allowing for a Union in XTCE. The issue arises that validating software cannot differentiate this with a bug in a container specification. A union tag or element of some sort is needed.