title: ERD - How to model a relation between two entites with a third entity as "attribute"
body: <p>I'm modeling an entity relationship diagram and got stuck. I'm not sure if my considerations are wrong or an ERD can't modell what I want:</p>
  
  <p>I have three entities: Employee, Project and Role. There is a relation between Employee and Project: an employee is working on a project. But this employee isn't just working on this project, he/she has a field of operation that is given as a role. But isn't a relation just described by attributes? How can I make something like "An employee works on this project as ..."? Of course I got use a roleId as an attribute as I would design it as a database, but what's the relation in an ERD?</p>