Variables

Jess exposes its two variable-resolution modes in the reference itself:

Reference	Meaning
$name	Live reference.
$$name	Scoped/final lookup.

Both $name: value and $$name: value create or update both bindings. $name?: tests live and creates or updates both if absent; $$name?: tests scoped/final and creates or updates both if absent. $name := updates live/current; $$name := updates scoped/final.

See Variables for the current reference contract and Namespaces and maps for the collection model.