a Array of expressions.

col_identifier (table): col@doc_path, tbl.col@doc_path col, tbl.col, schema.tbl.col col_identifier (document): doc_path .

DocumentPathItem .

Expressions the "root" of the expression tree .

function call: ``func(a, b, "1", 3)`` .

identifier: name, schame.name .

an object (with expression values).

operator: ``<<(a, b)`` .