Semantic Grammar
Semantic grammar lies between ELIZA and a more general English grammar. It uses a grammar in which nonterminal symbols have meaning in the domain of application.
<S>     -->  WHAT <CUST> ORDERED <PART>
              <MODS>
<CUST>  -->  CUSTOMER | CUSTOMERS <LOC>
<LOC>   -->  IN <CITY>
<CITY>  -->  AUSTIN | SEATTLE | LA
<PART>  -->  WIDGETS | WIDGET BRACKETS
<MODS>  -->  IN <MONTH> | BEFORE <MONTH>
<MONTH> -->  JANUARY | FEBRUARY | MARCH
WHAT CUSTOMERS IN AUSTIN ORDERED
  WIDGET BRACKETS IN MARCH
Advantages: