Legacy ID: #2928031
Legacy Poster: amitabh ojha (amitabhojha)
Researchers Jacky W.W. Wan and Gillian Dobbie (ACM, Jan 2004) have implemented the
well known Apriori Association Rule Mining Algorithm on XML data through XQuery, using
X-Hive/DB 4.1. My research work involves extending their published work. As a starting
point, I just tried to run their original XQuery on Saxon (after updating the syntax).
The XQuery code which is as follows, is contained in a single file
“apriori.xql” :- declare namespace my =
"urn:foo"; declare function my:join ($X, $Y) { let $items := for $item
in $Y where every $i in $X satisfies $i != $item return $item return $X union $items };
declare function my:commonIts ($X, $Y) { for $item in $X where some $i in $Y satisfies
$i = $item return $item }; declare function my:removeIts ($X, $Y) { for $item in $X
where every $i in $Y satisfies $i != $item return $item }; declare function
my:removeDuplicate ($C) { for $itemset1 in $C let $items1 := $itemset1/* let $items
:=(for $itemset2 in $C let $items2 := $itemset2/* where
$itemset2>>$itemset1 and count($items1) = count (my:commonIts ($items1,
$items2)) return $items2) where count ($items) = 0 return $itemset1 }; declare function
my:prune ($X, $Y) { every $item in $X satisfies some $items in $Y//items satisfies count
(my:commonIts (my:removeIts ($X, $item), $items/)) = count ($X) - 1 }; declare function
my:getLargeItemsets ($C, $minsup, $total, $src) { for $items in $C let $trans := (for
$tran in $src where every $item1 in $items/ satisfies some $item2 in $tran/* satisfies
$item1 = $item2 return $tran) let $sup := (count ($trans) * 1.00) div $total where $sup
>= $minsup return <largeItemset> {$items} <support>
{$sup} </support> </largeItemset> }; declare function
my:candidateGen ($l) { for $freqSet1 in $l let $items1 := $freqSet1//items/* for
$freqSet2 in $l let $items2 := $freqSet2//items/* where $freqSet2 >>
$freqSet1 and count ($items1) + 1 = count ($items1 union $items2) and my:prune
(my:join($items1,$items2), $l) return <items> {my:join ($items1, $items2)}
</items> }; declare function my:apriori ($l, $L, $minsup, $total, $src) {
let $C := my:removeDuplicate (my:candidateGen ($l)) let $l := my:getLargeItemsets ($C,
$minsup, $total, $src) let $L := $l union $L return if (empty ($l)) then $L else
my:apriori($l, $L, $minsup, $total, $src) }; let $src := doc
(“transactions.xml”)//items let $minsup := 0.4 let $total :=
count ($src) * 1.00 let $C := distinct-values ($src/) let $l := (for $itemset in $C let
$items := (for $item in $src/ where $itemset = $item return $item) let $sup :=
(count($items) * 1.00) div $total where $sup >= $minsup return
<largeItemset> <items> {$itemset} </items>
<support> {$sup} </support> </largeItemset>)
let $L := $l return <largeItemsets> {my:apriori($l, $L,$minsup, $total,
$src)} </largeItemsets> The file
“transactions.xml” is as follows :-
<transactions> <transaction id="1">
<items> <item>a</item>
<item>d</item> <item>e</item>
</items> </transaction> <transaction
id="2"> <items>
<item>b</item> <item>c</item>
<item>d</item> </items>
</transaction> <transaction id="3">
<items> <item>a</item>
<item>c</item> </items>
</transaction> <transaction id="4">
<items> <item>b</item>
<item>c</item> <item>d</item>
</items> </transaction> <transaction
id="5"> <items>
<item>a</item> <item>b</item>
</items> </transaction> </transactions> On
running this Xquery with Java SDK 1.4.2_04, using saxon7.jar (and also with saxon8.jar
and the JAXP 1.3 .jar files), the following error message shows up (even as the files
transactions.xml and the above XQuery are in the same sub-directory) :
“XQuery syntax error on line 82 in ‘ … := doc
(o^transactions.xmlö)// : Invalid Qname {o^transactions.xmlö} Except the recursive
apriori function, I have already tested all functions separately and found them ok. The
recursive apriori function is hard to test in isolation. Particularly worrying is that
once the above error shows up, thereafter even if you edit the portion of XQuery calling
code and make it only execute doc(“transactions.xml”), the
same error message comes up again. Will be really grateful if you could please test-run
this query and help me with further guidance.
Invalid QName error
.