title: Relationship between entity and relation in ER model and relational model?
body: <p>Can I set a relation between an entity and a many to many relationship on ER model? If so, how do you represent it?</p>
  
  <p>I read <a href="https://stackoverflow.com/questions/9138227/er-data-model-connecting-2-relations">ER data model (connecting 2 relations)</a> this but it just speaks about relational model...</p>
  
  <p>In my case I have a supermarkets DB. I will speak just about the entities with this problem:<br>
  -<em>Supermarket</em> sells <em>Product</em>.<br>
  -<em>Product</em> is sold on <em>Supermarket</em>.<br>
  -A <em>Supermarket</em> sells (0, n) <em>Product</em> and a <em>Product</em> is sold on (0, n) <em>Supermarket</em> : many to many relationship. <em>price</em> is a relationship attribute.<br>
  -<em>User</em> adds a <em>price</em> for a <em>Product</em> on an specific <em>Supermarket</em>.<br></p>
  
  <p>So can I add a relationship between <em>User</em> entity and <em>sells</em> relationship? How do you represent it on ER model?</p>
  
  <p>If not I should set a relationship between <em>Supermarket</em> and <em>Price</em> (in this case as a weak entity: it needs <em>Supermarket</em> as identifier) and another relationship between <em>Price</em> (weak entity) and <em>Supermarket</em> (strong entity).</p>
  
  <p>Thanks in advance.</p>