EQ is used in parsing equations embedded in scientific text:

                                +-----MVa-----+        
                                |     +---Xd--+---Xc--+
            +----Ss----+---Pvf--+     |   +-EQ+-EQ-+  |
            |          |        |     |   |   |    |  |
     Phosphorylation was.v observed.v ( P.eq =.v 0.06 ) 

The equals sign is marked as =.v because it behaves in a verb-like
manner ("the probability is 0.06"). It is also taken to be the
expression head, and is the point from which the equation connects 
to the "outside world", using MX- or MVa- links.

Expression parsing is fairly constrained and weak: equations must 
appear within parenthesis. Single letters and numbers can appear
in equations, as well as nouns, which are treated as "subjects" or
"objects".