You can't declare a node of being of type text and also having a list of other nodes in xsd, so this is a no for __href__. At least I don't know how.

What we can do instead is:

```xml
<href uri="/foo"/>

    <href route="acme_user_get" absolute="true">
        <parameter name="id">expr(object.getId())</parameter>
    </href>
```

Regarding the __parameter __ node, I'd like to have both nodes parameter and attribute of the same format. So I'd recommend that we also change the attribute node type.