"Logical refers to the relationships among the components of the relation, not to any arrangement of the components of a relation. Any presentation that preserves those relationships and adds no extra ones is acceptable. An R-table is one possible such presentation. The problem is that people fixate on this one presentation, identifying it with relation. They then go even further and force the physical implementation of a relation to be table-like." -- David McGoveranRead it all.
Please comment there, not here.