Can a set be indexed by another indexed set?

[DIUANA]

It is not possible to initialize a set that depends on previous initialized set that is indexed by an existing set.
Example:

scenario.init_set('a', idx_sets='technology')
scenario.init_set( "b", [ 'type_tec_land', 'a' ] )

This returns:
at.ac.iiasa.ixmp.exceptions.IxException: There exists no index set 'a'!

Is there another way to do that?

P.S.: Maybe it is more an ixmp issue. In that case I can close this one and open an issue there.

[khaeru]

I've transferred this to ixmp!

You're correct; this is not part of the data model. Either a set is a "simple" or "index" set (1-dimensional, not indexed by any other set) or it is complex (N-dimensional, with each dimension indexed by a simple set). Set a in your example is a hybrid.

A historical note: this distinction follows the data model of GAMS, since the first version of ixmp was tied to GAMS (we are working to relax this; see #78). But other software uses a similar distinction: see coordinates in xarray.

The solution in this case is:

scenario.init_set('a', idx_sets='technology')
scenario.init_set('b', [ 'type_tec_land', 'technology' ])

…and then use your own code to maintain the desired relationship between a and b.

Finally, there is one small issue here that is similar to #85: you should get a ValueError: indexed set 'a' cannot be an index of new set 'b' instead of the Java exception that is particular to the JDBCBackend. I will close this issue anyway, and make a note there to fix the two together.

[DIUANA]

Thanks Paul