Feature Terms

It is possible to associate to a symbol (say employee) a list of features (say [name,job,salary]). When building a term based on employee, it is not necessary to assign explicitely and in order a value for all its features because the missing values will be filled by new anonymous variables. For instance, the feature term employee{salary=>6000,name=>john} is equivalent to the term employee(john,_,5000). Note the use of enclosing {} instead of enclosing () to mark feature terms.

To associate a feature table to a symbol, use the directive features/2.

     :-features(employee,[name,job,salary]).
     

It is also possible to use Typed Feature Structure, following the same syntax.