ALPS document w/ various examples of the `def` element

def-sample.xml

<alps>
  <doc>Sample Service</doc>

  <!-- properties -->
  <descriptor id="identifier" def="https://schema.org/identifier" />
  <descriptor id="givenName def="https://schema.org/givenName" />
  <descriptor id="familyName def="https://schema.org/familyName" />
  <descriptor id="status" def="https://schema.org/status" />
  <descriptor id="dateCreated" def="https://schema.org/dateCreated" />
  <descriptor id="dateModified" def="https://schema.org/dateModified" />

  <!-- actions -->
  <descriptor id="collection" type="safe" rt="#record" 
    def="https://tools.ietf.org/html/rfc6573#section-2.2" />
  <descriptor id="item" type="safe" rt="#record"
    def="https://tools.ietf.org/html/rfc6573#section-2.1" />
  <descriptor id="search" type="safe" rt="#record"
     def="https://www.iana.org/assignments/link-relations/link-relations.xhtml" />
  <descriptor id="create-form" type="unsafe" rt="#record" 
    def="https://tools.ietf.org/html/rfc6861#section-3.1" />
  <descriptor id="edit-form" type="idempotent" rt="#record" 
    def="https://tools.ietf.org/html/rfc6861#section-3.2" />
  <descriptor id="remove" type="idempotent" rt="#record"
    def="http://rels.amundsen.com/remove" />

  <!-- containers -->
  <descriptor id="record">
    <descriptor href="#identifier" />
    <descriptor href="#givenName />
    <descriptor href="#familyName />
    <descriptor href="#status" />
    <descriptor href="#dateCreated"  />
    <descriptor href="#dateModified" />
  </descriptor>
  
</alps>