Experimenting with AFIncrementalStore and it is pretty sweet. However I've come across a scenario I am not entirely sure how to deal with.

I have a model that returns an id of a child relationship, but not the content itself. eg: 
GET /groups

```
{"id":3,"description":"My Group","category_id":2}

```

I can get all the categories with a regular GET /categories. But I do NOT have a call to GET /group/3/categories

So what I don't know is how I can initialize the child relationship of the group.category. I'm sure I'm missing something obvious, but any help would be greatly appreciated.

Any suggestions?