Comparing elements by attribute in Xquery

Question

so far I have an XML document called resume that, among other things, contains skill elements in the following manner:

    <skills>
        <skill what = "C" level="0"></skill>
        <skill what = "Java" level="1"></skill>
        <skill what = "SQL" level="2"></skill>
        <skill what = "Lisp" level="3"></skill>
    </skills>

The objective of my query I want to run is the following: I want to find pairs of resumes that possess exactly the same number of skills, and that match in both "what" and "level", and output results such as this:

resume1, resume2 resume1, resume3

This is the query I have written:

for $r1 in $resumes/resumes/resume, $r2 in $resumes/resumes/resume


where $r1/@rID != $r2/@rID and count($r1/skills/skill) = count($r2/skills/skill) 


return ($r1,$r2) 

I need help in actually comapring both $r1 and $r2's @what and @level. I have tried with

data($r1/@what) = data($r1/skills/skill/@what) along with data($r1/skills/skill/@level) = data($r2/@level)

but i can't seem to get the desired output. Is there a way to make this comparison? Thanks very much.

Note: I am using XML 1.0

Answer 1

By reformulating your problem to find skills, that only one of them has , the problem gets rather easy to solve.

let $skills1 :=    <skills>
        <skill what = "C" level="0"></skill>
        <skill what = "Java" level="1"></skill>
        <skill what = "SQL" level="2"></skill>
        <skill what = "Lisp" level="3"></skill>
        <skill what = "XQuery" level="4"></skill>
    </skills>
let $skills2 :=    <skills>
        <skill what = "C" level="0"></skill>
        <skill what = "Java" level="1"></skill>
        <skill what = "SQL" level="2"></skill>
        <skill what = "Lisp" level="3"></skill>
    </skills>

return
  for $skill in ($skills1, $skills2)/skill
  where not(
    $skills1/skill[deep-equal(., $skill)] and
    $skills2/skill[deep-equal(., $skill)]
  )
  return $skill

This will return the skill that is only in skill set 1 (XQuery with level 4). If you wrap the whole flwor-expression in the return clause in an empty(...) call, you will get true for matching skill sets, or false if they have (any) uncommon members.