update canned-queries: start adding some contextual comments

canned-queries.xq

@@ -1,7 +1,19 @@
-(: some helpful queries :)
+(: some helpful queries --
+ : these can be run in the BaseX GUI, by copying the query up to the delimiting ',' (comma -- but *not* the comma!)
+ : into a new file and then running the file.
+ :
+ : assumptions:
+ : 1) you have similarly named databases!
+ : 2) you're using BaseX
+ :)
 
+(:
+ : the following query returns the OAI-PMH identifier for each record with an attribute='deleted', appearing anywhere in
+ : the record.
+ :)
 for $name in db:open('repox-sets')/set/spec/text() return db:open($name)/*:record[//@*='deleted']/*:header/*:identifier/text(),
 
+
 for $name in db:open('repox-sets')/set/spec/text() return db:open($name)/*:record[*:header/*:identifier[fn:contains(.,'p265301coll005/7')]],
 
 for $name in db:open('repox-sets')/set/spec/text() return db:open($name)/*:record[*:header/*:identifier[fn:contains(.,'p18877coll16/24')]],