Re: "[flexible schema change is a] huge problem with SQL in general." -- I've been a proponent of the idea of "dynamic relational". You can add any column on wh

Re: "[flexible schema change is a] huge problem with SQL in general." -- I've been a proponent of the idea of "dynamic relational". You can add any column on whim to a row just by including it in an INSERT or UPDATE command, unless an explicit constraint/rule forbid it for a given table or database. You could even make tables similarly create-on-write. No DBA's needed! (within reason) Comparisons have to be done with care, though, as with any dynamic/implied typed system. But create-on-write doesn't solve cross-table relationship flexibility problems: such as changes between 1-to-1 to 1-to-many and/or to many-to-many. If you already have data, that's usually a tricky domain problem regardless of what kind of database technology you use. It's about the semantics of your data, not machines.