public interface TaskInputExpression
A TaskInputExpression is a String prefixed with either "$input" or "$inputRecord",
followed by an optional dot-separated hierarchical path, which can specify either an
atomic data value (String, Number) or Record from the input data. For example, if the
Process.state represented in JSON
were:
{
orderId:5,
orderItems: [
{name:"Pencils", quantity:3, itemId:2344}
],
orderUser: { name:"Henry Winkle", address:"...", ... }
}
.. and a task specified an inputField of "orderId" and an inputFieldList of
"orderItems","orderUser", then: