anchor.diff:    ?person v:age ?age . }""")
   ----
   
  -[[pattern-matching]]
   ==== Pattern Matching
   
   Select only those persons who created a project.
  
positive.code: g.sparql("""SELECT * WHERE { }""")
  ----
  
  [[match-constant-values]]
  ==== Match Constant Values
  
  Select all vertices with the label `person`.
  
negative.code:     FILTER (?age > 30 && ?lang = "java") }""")
  ----
  
  ==== Union
  
  Select all persons who have developed a software in java using union.
  