anchor.diff:  } ORDER BY (?age)
   ----
   
  -Pattern Matching using Query modifier - Group By
  -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  -
  -TBA
  +Query modifier - Group By
  +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  +
  +.Select all vertices with the label `person` and group them by their age.
  +----
  +SELECT * WHERE {
  +  ?person v:label "person" .
  +  ?person v:age ?age .
  +} ORDER BY (?age)
  +----
  +
  +
  + SPARQL queries with Group By + Count
  +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  +
  +example coming soon
  +
  +
  +
  +SPARQL mixed/complex/aggregation-based queries 
  +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  +
  +example coming soon
  +
  +
  +SPARQL Star-shaped queries 
  +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  +
  +example coming soon
  +
  +
  +Limitations
  +-----------
  +
  +1. Gremlinator currently only supports SPARQL 1.0 specification
  +2. SPARQL queries with variables in the predicate position are not currently covered, with an exception of the following case:
  +----
  +SELECT * WHERE { ?x ?y ?z .}
  +----
  +
  +
  +Future work
  +-----------
  +1. cover all cases of SPARQL queries with variables in predicate position
  +2. cover SPARQL 1.1 specification (such as Property Paths)
  +
  
positive.code: }
  ----
  
  Pattern Matching Union Queries
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  .Select all persons who have developed a software in java using union.
  
negative.code: }
  ----
  
  
   Optional Queries
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  coming soon
  
  
  
  Query modifier - Order By
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  .Select all vertices with the label `person` and order them by their age.
  [source,SPARQL]
  ----
  SELECT * WHERE {
  