There are various approaches to the problem. Take for example the voltage (

vsource.sym

) source, it has just a 'value' attribute, that value can be anything from a simple '`1.8`' to a more complex '`pwl 0 0 100n 101n 1,8`' or '`pulse 0 1.8 0 1n 1n 10n 40n`' or anything else that the simulator understands. It could be easy to create specialized voltage sources, like

vsin

,

vpulse

,

vpwl

,

vdc

, with specific meaningful attributes. For example the '`vsin`' source could have '`amplitude`

offset

frequency

`delay`' and so on. Similarly for simulator commands , instead of a 'code.sym' element where one writes the testbench it could be easy to add symbols for specific simulator setups. I am guessing every designer has his personal preferences about these UI aspects. People with sw background normally prefer free coding, the other might prefer a more guided and constrained UI interface. The other thing i want to be careful about is that xschem is simulator agnostic, it should work (with some necessary testbench modifications) with ngspice, xyce, hspice, finesim, spectre and others.