This is not actually a VEDA issue.
The dimensions of the reporting parameters are defined in the file Times2Veda.vdd. Initially (in 2004), they appear to have been defined to be the following:
[Dimensions]
Attribute attr
Commodity c
Process p
Period t
Region r
Vintage v
TimeSlice s
However, then someone thought that it would be nice to have the user constraint marginals reported as well. Consequently, in 2006 the new dimension UserConstraint (uc_n) was added at the end.
Nonetheless, over time there were further requests for new reporting parameters. At that point, there were already so many VEDA-BE databases in use that it would probably have caused problems to add more dimensions (and it would also make the databases bigger).
Therefore, the UserConstraint dimension has basically become as an Other_indexes dimension, which is used by the following reporting attributes not related to UC_N:
- VAR_NcapR - for the name of the cost/benefit indicator
- EQ_IreM - for IMP/EXP
- Cap_New - for the name of the reporting indicator (LUMPINV, INSTCAP)
- Cost_Inv - for the hurdle rate indicator
- Cost_Invx - for the hurdle rate indicator
- Cost_NPV - for the hurdle rate indicator
- Time_NPV - for the annualising type indicator
- Reg_wobj - for the objective component indicator
- Reg_ACost - for the objective component indicator
It would be easy to change the name of the dimension in the file
Times2Veda.vdd (you could even do that by yourself). But I suspect that you would then no longer be able to import new results into existing databases, and that's why it has not been renamed thus far.