Practical Grammar 8

The Difference between Defining Equations and Constraining Equations

There are several types of equations that can be used in annotations. So far, we have encountered the following two:

(1) ↑=↓1;
(2) (↑ OBJ) =↓2;

These equations are both defining equations.

Defining equations add their information to an f-structure.

There is a second kind of equation, which we have not seen yet, but which you will need for the following exercise. These are called constraininig equations.

Constraininig equations test whether their information is contained in an f-structure. They do NOT add the information themselves.