title: Modelling "services" in a uml class diagram
body: <p>In one on my software engineering homework i need to make the class diagram for modelling the problem of develop a system for a public library that can manage its <strong>loan service</strong>.</p>
  
  <p>In this scenario i have an <strong>user</strong>, that can loan trough a <strong>loan service</strong> some library material (like audio dvd, video, text like book or something else).
  This is the rapid blueprint:
  <img src="https://i.ibb.co/ThXk4sV/class.jpg" alt="ciao">
  Now my questions are:</p>
  
  <p><strong>Q1</strong>: How can i model the association between user and the loan service? and , exactly, what is the name of this association?</p>
  
  <p><strong>Q2</strong>: The loan service class only have one istance, because i think that the service is global for all user, so is correct to modelling this in the cardinality of the association?</p>
  
  <p>Thank's in advance.</p>