Sentence:  When the subgraph is a <WSD>hyperloop</WSD>, the associated equation is a relation involving no variables: in the unfrustrated case, it is just a trivial identity; in the frustrated case, it is a configuration-independent characteristic of the instance which could eventually determine a priori unsatisfiability. 
Meaning of the word marked with <WSD> tags:  A quantum mechanical paradox resulting from the observer being a product of the observations that it makes.