It would make development even easier and faster in a lot of cased, if there is an option to retrieve an associated entity with xpath options.
e.g. object is to retrieve an attribute, which has the key "birthday" of a person:
$person/attribute[key=value]
This can be thought further, if this function could be used to set variables or arguments.
e.g. $person/attribute[key=birthday]/date
It can be even thought further if this can be used to filter/find entities in a list.