Extend expression language

[Silvanoc]

Current expression language has poor support for handling lists (only the equivalent to a python list comprehension like following is supported: [item.field for item in items]). It would be useful to have more advanced possibilities.

The language is declarative and should remain like that. Python list comprehensions are also declarative, but too bound to python. A more programming-language independent specification would be desirable.

jq could be taken as an expression language inspiration/reference (as proposed by @cmungall) or even simply taken over... we could then use the available implementation. Since instances can be serialized as JSON and jq can be integrated into python, why not directly extend it that way?