gistfile1.js

Species = DS.Model.extend({
  name: DS.attr('string')
});

Person = DS.Model.extend({
  name: DS.attr('string'),
  species: DS.belongsTo(Species, { embedded: true })
  tags: DS.hasMany(Tag, { embedded: true })
});

person = store.load(Person,1,{id:1, species:{id:1, name:"Human"}});
machine = store.load(Species,2,{id:2, name:"Machine"});

// person.getPath('species.name') === "Human"
person.set('species', machine);
// person.getPath('species.name') === undefined
//                        should  === "Machine"