title: Can the entities (a,b,c,t1,x,y,z) and (a,b,c,t2,x,y,z) exist both at the same time?
body: <p>Suppose we have two entity sets, A, with attributes a,b,c and B, with attributes x,y,z, and also a relationship between them C, with attribute t.</p>
  
  <p>It it possible for the entities (a,b,c,t<sub>1</sub>,x,y,z) and (a,b,c,t<sub>2</sub>,x,y,z) to exist at the same time in the ER model? </p>
  
  <p>I think that since "t" is an attribute of the relation between them, it should not count, so it should not be possible. Is this right?</p>