thing1 thing2 thing3 var4 var5 var6 var7 var8 var9 var10 var11 var12 var13 http://example.com/system2/rel1 thing1 var4 http://example.com/system2/rel2 thing1 var5 http://example.com/system2/rel3 thing1 var12 http://example.com/system2/rel4 thing3 thing2 http://example.com/system2/rel5 thing2 thing1 http://example.com/system2/rel6 thing3 var6 http://example.com/system2/rel7 thing3 var7 http://example.com/system2/rel8 thing3 var13 var13 X http://www.w3.org/2005/xpath-functions/#starts-with var6 lit5 var12 1 var12 2 http://example.com/system2/rel9 thing3 var10 http://example.com/system2/rel10 thing3 var11 var10 null http://www.w3.org/2005/xpath-functions/#numeric-greater-than var11 0 http://example.com/system2/rel11 thing3 var8 thing14 http://example.com/system2/rel12 thing14 thing3 http://example.com/system2/rel13 thing14 X thing15 http://example.com/system2/rel14 thing15 var6 http://example.com/system2/rel15 thing15 var5 http://example.com/system2/rel16 thing15 X thing16 thing17 http://example.com/system1/rel1 thing16 thing17 http://example.com/system1/attribute/name thing17 var4 thing18 var19 http://example.com/system2/rel17 thing3 thing18 http://example.com/system2/rel18 thing18 var19 var19 null var9 thing20 thing21 thing22 var23 var24 var25 http://example.com/system1/rel2 thing21 var4 http://example.com/system1/rel3 thing21 true http://example.com/system1/rel4 thing21 var23 http://www.w3.org/2005/xpath-functions/#starts-with var23 lit4 http://example.com/system1/rel2 thing22 var6 thing26 thing27 http://example.com/system1/rel2 thing27 var6 http://example.com/system1/rel5 thing26 thing27 http://example.com/system1/rel6 thing26 thing22 http://example.com/system1/rel6 thing26 thing27 http://example.com/system1/rel5 thing26 thing22 thing28 thing29 thing30 http://example.com/system1/rel7 thing30 thing21 http://example.com/system1/rel8 thing28 thing30 http://example.com/system1/rel2 thing29 var6 http://example.com/system1/rel9 thing30 thing22 http://example.com/system1/rel10 thing28 thing29 http://example.com/system1/rel9 thing30 thing29 http://example.com/system1/rel10 thing28 thing22 http://example.com/system1/rel1 thing20 thing21 http://example.com/system1/rel11 thing20 thing22 http://example.com/system1/rel12 thing20 var5 http://example.com/system1/rel13 thing20 var7 http://example.com/system1/rel14 thing20 var24 var9 lit1 var24 lit1 http://example.com/system1/rel15 thing22 lit2 http://example.com/system1/rel16 thing22 var25 http://www.w3.org/2005/xpath-functions/#starts-with var25 lit3 Certain constellations of data in system 2 must be valid with respect to corresponding constellations of data in system 1.