A variable read through a chain of accessors: ?x, SUBJECT(?x), OBJECT(SUBJECT(?x)).
An assertion is about an access rather than a variable, since a triple term is constrained one position
at a time. The chain reads left to right from the root, so { name: 'o', positions: [ 'subject', 'object' ]} is OBJECT(SUBJECT(?o)), and the zero-length access is the variable itself.
A variable read through a chain of accessors:
?x,SUBJECT(?x),OBJECT(SUBJECT(?x)).An assertion is about an access rather than a variable, since a triple term is constrained one position at a time. The chain reads left to right from the root, so
{ name: 'o', positions: [ 'subject', 'object' ]}isOBJECT(SUBJECT(?o)), and the zero-length access is the variable itself.