anchor.diff:      + entity (required, string `<http://purl.obolibrary.org/obo/BFO_0000050> some <http://purl.obolibrary.org/obo/UBERON_0008897>`) ... Anatomical class expression in [OWL Manchester syntax](http://www.w3.org/TR/owl2-manchester-syntax/)
       + variable_only (optional, boolean, `true`) ... whether to restrict the matrix to characters with both 'present' and 'absent' values in the matrix
   + Response 200 (application/xml) 
  +
  +# Group Semantic Similarity
   
   ## Semantic similarity query [/similarity/query{?iri,limit,offset}]
   ### Retrieve taxon variation profile similarity scores for this gene, ordered with best matches first [GET]
  
positive.code:         "expect_score": 0.00352135614022
          }]
          }
  
  ## Genes affecting phenotype [/genes_affecting_phenotype{?entity,quality}]
  ### Search for genes affecting phenotype of any part of a structure [GET]
  
negative.code:             "label": "basihyal bone"
          }]
          }
          
  
  # Group OntoTrace
  
  ## OntoTrace [/ontotrace{?taxon,entity,variable_only}]
  ### Generate matrix of inferred presence/absence associations for anatomical structures subsumed by the provided entity class expression, for any taxa within the provided taxon class expression [GET]
  Returns a NeXML-format evolutionary character matrix.
  + Parameters
  