A pretty idiomatic (and trivial to implement) Scala way of doing this would be to have a DSL with a name for each relation and compose them together using funct

A pretty idiomatic (and trivial to implement) Scala way of doing this would be to have a DSL with a name for each relation and compose them together using function application. So to express "MothersSiblingsDaughter" you'd write "mother sibling daughter". The whole expression would return an object which contains a linked list of the individual components, consed together by each individual function application in the chain. Of course, this is kind of co-opting the call stack to build up at runtime what the compiler can already provide as an AST, so it might be better to just use a macro. This representation can't be serialized quite as easily as a single symbol or whatever Apple is doing, but it is infinitely flexible. And it seems like a code smell to me that they have a special case for the father's brother, while the mother only has a generic "sibling." It should be up to the view layer to determine that kind of localization-specific logic. If you just store a completely arbitrary relation then you can punt it to the localization to decide how to translate that into meatspeak.