Non-embeddable relational configurations
  Relational configurations are defined by the relationships between systems. Individualist configurations are defined by the properties of individual systems. Non-embeddable relational configurations are those for which there is no equivalent individualist description. We suggest that situations in physics where a spacetime description breaks down may be the result of trying to use individualist configurations to model non-embeddible relational configurations. We propose a particular example of a relational configuration space, the 2 instant relation (2IR), whose embeddible configurations describe particle worldlines in a background spacetime. We investigate the properties of these configurations. 
William Edwards
gr-qc