anchor.diff:  <p>
   Each problem domain may have one or more <em>variants</em>, which concern
   different manners of implementation or random instance generation.  E.g., the
  -traffic of Dubins cars domain (cf. Section 7) has a simulation variant, which
  +traffic of Dubins cars domain has a simulation variant, which
   relies on Gazebo, and a physical variant, which involves a real testbed of
   several Kobuki bases as well as an overhead pose tracking system.
   </p>
  
positive.code: </p>
  
  <p>
  There are three <em>problem domains</em>, which are described in Sections 6, 7,
  and 8 (one per section).  Within a problem domain, a problem
  <em>instance</em> is a particular workspace, arrangement of obstacles, labeling
  of the workspace, selection of parameters for the robot dynamics, and a task
  formula.
  
negative.code: the <a href="http://api.fmrchallenge.org">API manual</a>.
  </p>
  <p>
  <a href="releases/fmrchallenge-v0.0.4.pdf" class="importantlink">Get the current release</a>, which corresponds to <a href="https://github.com/fmrchallenge/fmrbenchmark/releases/tag/v0.0.4">version 0.0.4</a> of the <a href="https://github.com/fmrchallenge/fmrbenchmark">fmrbenchmark repository</a>.
  </p>
  
  <h3>terminology</h3>
  