XML DTD - xPath 1.0

Question

I have this dtd:

<!ELEMENT db (obj, prop*)>
<!ELEMENT obj (obj*)>
<!ATTLIST obj
    id ID #REQUIRED
>
<!ELEMENT prop (#PCDATA)>
<!ATTLIST prop
    objs IDREFS #REQUIRED
>

I need to write a xPath, which return all "prop"s, where "objs" contains of "obj"s with children. For example:

<db>
    <obj id="a007">
    <obj id="a008"> </obj>
        <obj id="a009">
            <obj id="a011"> </obj>
        </obj>
    </obj>   
    <obj id="a011"> </obj>
    <prop objs="a007 a011">
        "first"
    </prop>
    <prop objs="a007">
        "second"
    </prop>
    <prop objs="a009 a007">
        "third"
    </prop>
</db>

a want it return second and third.

Answer 1

Try the path /db/prop[not(id(@objs)[not(obj)])], it selects those prop element child nodes of the db root element where id(@objs) does not find an element not having an obj child.