<sparql xmlns='http://www.w3.org/2005/sparql-results#'>
<head>
<variable name='x'/>
<variable name='y'/>
</head>
<results>
<result>
<binding name='x'><uri>http://www.example.org/instance#a</uri></binding>
<binding name='y'><uri>http://www.example.org/instance#b</uri></binding>
</result>
</results>
</sparql>
