var schema = new Schema({
  foo: { type: String, alias: 'bar' } // Create virtual getter/setter
});

var Schema = mongoose.Schema;
var TestSchema = new Schema({
  foo: { type: String, alias: 'Faa' },
  bar: {
    baz: { type: String, alias: 'Baa' },
    kar: { type: String, alias: 'Kaa' }
  }
});
var Test = mongoose.model('Test', TestSchema);
var test = new Test({
  foo: 'a',
  bar: {
    baz: 'b',
    kar: 'c',
  }
});

assert.equal(test.foo, test.Faa);
assert.equal(test.bar.baz, test.Baa);
test.Kaa = 'd';
assert.equal(test.bar.kar, test.Kaa);