This function that returns a Domain has the side-effect of declaring x and y:

MyPair(T:Domain):Domain==Record(x:T,y:T)

   Function declaration MyPair : Domain -> Domain has been added to
      workspace.

w:MyPair(Float)

   Cannot compile the declaration for x because its (possible partial)
      type contains a local variable.
   OpenAxiom will attempt to step through and interpret the code.

Compiling function MyPair with type Domain -> Domain 
   Compiled code for MyPair has been cleared.

x

   x is declared as being in Float but has not been given a value.
y

   y is declared as being in Float but has not been given a value.
w

   w is declared as being in Record(x: Float,y: Float) but has not been
      given a value.

But this does not happen for Union

MyAlt(T:Domain):Domain==Union(p:T,q:T)

   Function declaration MyAlt : Domain -> Domain has been added to
      workspace.

r:MyAlt(Float)

   Cannot compile the declaration for p because its (possible partial)
      type contains a local variable.
   OpenAxiom will attempt to step through and interpret the code.

Compiling function MyAlt with type Domain -> Domain

p

(1)

q

(2)

r

   r is declared as being in Union(p: Float,q: Float) but has not been
      given a value.