anchor.diff:  Freshness = 50
   
   [[operation]]
  -Operation
  -~~~~~~~~~
  +=== 2.3 Operation
   
   Operation represents the degree of the maintenance. We send HTTP request
   to the endpoint URI with using the accept request-header field to
  
positive.code:   \right.$]
  
  [[validity]]
  Validity
  ~~~~~~~~
  
  Validity represents how endpoint and data in it obey the rules. We
  measure the two metrics:
  
negative.code: In Section [metrics], we show how to score endpoints from each aspect.
  
  [[metrics]]
  == 2. Metrics of Umaka Score
  
  [[availability]]
  === 2.1 Availability
  
  Availability represents the degree of ready for use. High availability
  value means we can access the endpoint most of all the time. Low
  