Path notation
.............

Often, variables appear in the condition of productions only to link the
value of one attribute with the identifier of another attribute.  Attribute
path notation provides a shorthand so that these intermediate variables do
not need to be included.  Using path notation, a sequence of attributes are
separated by dots ("."), after the "^" in a condition.  So instead of writing
^attr value, you can write ^attr.attr.attr value.

For example,

(sp propose-operator*extinguish-hair
  (goal <g> ^problem-space.name acid-trip ^state.hair-status flaming)
 -->
  (<g> ^operator <o> +)
  (<o> ^name extinguish-hair))

is treated as meaning

(sp propose-operator*extinguish-hair
  (goal <g> ^problem-space <p*1> ^state <s*1>)
  (<p*1> ^name acid-trip)
  (<s*1> ^hair-status flaming)
 -->
  (<g> ^operator <o> +)
  (<o> ^name extinguish-hair))

where <p*1> and <s*1> are new variables not occurring elsewhere
in the production.  

Path notation is currently not supported for actions.  Also, don't use any
path components that start with a digit.  For example, if you type
^foo.3.bar, Soar thinks the .3 is a floating-point number.