Issue 8909: lack of Union construct  (MER + ASIST) (xtce-rtf)
Source: NASA (Mr. Kevin Rice, james.k.rice-1(at)nasa.gov)
Nature: Uncategorized Issue
Severity: 
Summary: 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.


Resolution: 
Revised Text: 
Actions taken:
June 21, 2005: received issue
Discussion: 
Resolution:
ASIST noted that Unions could be 'faked' using the locationInContainer mechanism and at this point doesn't seem to want anything more.  This may not be true in the future however.  The problem with this is deriving unions from the entryLists then, you have to analyze the locationInContainer area and find overlaps,  then one has decide whether the overlapping parameters are unions or just typos. Deferred is fine for now.  

End of Annotations:=====
s is issue # 8909

lack of Union construct  (MER + ASIST)

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.