Web interface to generate logical relationships

I need to design and implement a form by which user can define logical relations between some predefined elements.

Imagine there are 5 predefined elements named E1, E2, E3, E4 and E5 (in final product, there are many more). Logical relationships (AND/OR/NOT) should connect them in any way that user demands. For example, user must be able to create any of the bellow lines using the mentioned form:

E1 AND E2 AND E3 OR E4 OR E5

(E1 AND E2) AND (E3 OR E4 OR E5)

E1 AND (E2 AND E3) OR (E4 OR E5)

I need help on designing its interface. Is there any sample you could introduce that does so while is meaningful to end-user?

Any help is appreciated