]> Note that adjacent_to as thus defined is not a symmetric relation, in contrast to its instance-level counterpart. For it can be the case that Cs are in general such as to be adjacent to instances of C1 while no analogous statement holds for C1s in general in relation to instances of C. Examples are: nuclear membrane adjacent_to cytoplasm; seminal vesicle adjacent_to urinary bladder; ovary adjacent_to parietal pelvic peritoneum adjacent_to relationship http://sswapmeet.sswap.info/obo/owl/PMID#PMID_15892874 PMID:15892874 C adjacent to C' if and only if: given any instance c that instantiates C at a time t, there is some c' such that: c' instantiates C' at time t and c and c' are in spatial proximity