XQuery. Error: unknown function - function

Question

I have an assignment:
Define the co-author graph G of the dblp-excerpt to be the undirected graph that has all authors as nodes, such that there is an edge between author a and author b in G if and only if a and b have written a publication together.
Define the distance between two authors a and b to be the length of the shortest path between a and b in G. Hence, authors that have published together have distance 1.
Moreover, if a and b have not published together but they have both published together with c, then the distance between a and b is two. Write an XQuery program that computes, for each pair of authors x and y 6= x the distance
between x and y using the following output format.
I wrote a code, but it doesn't work. I'm sure, it is very simple mistake, but I can't find it.
I have an error: Error:
Stopped at C:/Users/Zhanna/Desktop/Test/test_3.xq, 28/44: [XPST0017]
Unknown function 'local:getAvailablePathSizes'.
It underlines the beginning of the list of arguments in line 28, which is:
return
local:getAvailablePathSizes($graph,$current,$target,$visitedList,$count+1)
I validate the query with the Saxon as well and it also give a msg like this:
Error XPST0008: Unresolved reference to variable $count Static
error(s) in query
Help me, please, to fix it.
<ee>
let $graph:=(
<graph>{
for $a in distinct-values(//author)
let $publications:=/dblp/*[author=$a]
order by $a
return
<node name="{$a}">
{
let $co:=$publications/author[(.)!=$a] return
for $distinctCo in distinct-values($co) return
<edge from="{$a}" to="{$distinctCo}"/>
}
</node>
}</graph>
) return
declare function local:getAvailablePathSizes
($graph, $start, $target, $visitedList, $count)
{
let $cos:=$graph/node[#name=$start]/edge/#to return
let $listOfDistances:=(
for $current in $cos
return
if($current=$target) then $count+1 else
if (empty(visitedList[.=$current])) then(
let $visitedList:=insert-before(data($current), 0, $visitedList)
return local:getAvailablePathSizes($graph,$current,$target,$visitedList,$count+1)
) else()
)
return $listOfDistances
};
<distances>
{
for $node in $graph/node return
for $to in $graph/node[#name!=$node/#name]
let $dist:=min(local:getAvailablePathSizes($graph, $node/#name, $to/#name, null, 0))
return
if($dist>0) then(
<distance
author1="{$node/#name}"
author2="{$to/#name}"
distance="{$dist}"/>)
else()
}
</distances>
</ee>
This is the XML file
http://www.filedropper.com/dblp

Answer 1

The first problem is, that you did omit curly braces around the XQuery code inside the <ee> element, so large parts of your code haven't been evaluated (but interpreted as text instead). This resulted in a barely helpful error message indicating the second problem: you must define functions in the so-called prolog before the "normal" XQuery statements (in the query body).
declare function local:getAvailablePathSizes
($graph, $start, $target, $visitedList, $count)
{
let $cos:=$graph/node[#name=$start]/edge/#to return
let $listOfDistances:=(
for $current in $cos
return
if($current=$target) then $count+1 else
if (empty(visitedList[.=$current])) then(
let $visitedList:=insert-before(data($current), 0, $visitedList)
return local:getAvailablePathSizes($graph,$current,$target,$visitedList,$count+1)
) else()
)
return $listOfDistances
};
<ee>{
let $graph:=(
<graph>{
for $a in distinct-values(//author)
let $publications:=/dblp/*[author=$a]
order by $a
return
<node name="{$a}">
{
let $co:=$publications/author[(.)!=$a] return
for $distinctCo in distinct-values($co) return
<edge from="{$a}" to="{$distinctCo}"/>
}
</node>
}</graph>
) return
<distances>
{
for $node in $graph/node return
for $to in $graph/node[#name!=$node/#name]
let $dist:=min(local:getAvailablePathSizes($graph, $node/#name, $to/#name, null, 0))
return
if($dist>0) then(
<distance
author1="{$node/#name}"
author2="{$to/#name}"
distance="{$dist}"/>)
else()
}
</distances>
}
</ee>