Models -- Validation of Graph Characteristics

[Jack_W]

In 0.9, where do you validate such graph-related constraints as, for example, an added or changed relationship must not form a loop, or must not add a root? The caller could have commanded the change by calling a relationship assignment method, e. g., parent=, or by adding to a collection proxy, e, g., foo.children << bar. In a case like that, should foo.children and bar.parent both have validators slapped onto them? And how do the validators cope with the possible discrepancies between what the cache says and what the database says? The cache doesn't even seem maintain consistency with itself in the face of changes when it comes to the reciprocal acknowledgement of relationships. How do the validators cope with the possible self inconsistency of the cache?