Semantic Grammar: Extended Pattern Matching

In this approach, the pattern-matching that is allowed is restricted to certain semantic categories. A grammar is used to specify the allowable patterns; this allows the restrictions to be specified easily, while allowing more language coverage and easier extension with fewer specified patterns.

Example:

<s> --> what is <ship-property> of <ship>? 
<ship-property> --> the <ship-prop> | <ship-prop> 
<ship-prop> --> speed | length | draft | beam 
<ship> --> <ship-name> | the fastest <ship2> 
           | the biggest <ship2> | <ship2> 
<ship-name> | Kennedy | Kitty Hawk | Constellation
<ship2> --> <countrys> <ship3> | <ship3> 
<ship3> --> <shiptype> <loc> | <shiptype> 
<shiptype> --> carrier | submarine | ... 
<countrys> --> American | French | British
<loc> --> in the Mediterranean | in the Med | ...

"What is the length of the fastest French sub in the Med?"