Hello Dr. Grün, I open the database 'Collection' in the basex tool and enter the following query for $x in collection('Collection')return $x//PoetSession and get the following error message under Query Info.If you want I can provide you with the database files. Kind regards, Achim. Error:Improper use? Potential bug? Your feedback is welcome:Contact: basex-talk@mailman.uni-konstanz.deVersion: BaseX 7.9Java: Sun Microsystems Inc., 1.6.0_21OS: Windows XP, x86Stack Trace: java.lang.RuntimeException: Data Access out of bounds:- pre value: 75055- #used blocks: 294- #total locks: 294- access: 293 (294 > 293] at org.basex.util.Util.notExpected(Util.java:53) at org.basex.io.random.TableDiskAccess.cursor(TableDiskAccess.java:508) at org.basex.io.random.TableDiskAccess.read1(TableDiskAccess.java:194) at org.basex.data.Data.kind(Data.java:284) at org.basex.query.value.node.DBNode.<init>(DBNode.java:53) at org.basex.query.value.seq.DBNodeSeq.itemAt(DBNodeSeq.java:65) at org.basex.query.value.seq.DBNodeSeq.itemAt(DBNodeSeq.java:19) at org.basex.query.value.seq.Seq$1.next(Seq.java:92) at org.basex.query.gflwor.For$1.next(For.java:71) at org.basex.query.gflwor.GFLWOR$2.next(GFLWOR.java:74) at org.basex.query.MainModule$1.next(MainModule.java:98) at org.basex.query.QueryContext.execute(QueryContext.java:580) at org.basex.query.QueryProcessor.execute(QueryProcessor.java:101) at org.basex.core.cmd.AQuery.query(AQuery.java:82) at org.basex.core.cmd.XQuery.run(XQuery.java:22) at org.basex.core.Command.run(Command.java:329) at org.basex.core.Command.execute(Command.java:94) at org.basex.gui.GUI.exec(GUI.java:417) at org.basex.gui.GUI.access$500(GUI.java:41) at org.basex.gui.GUI$8.run(GUI.java:361)Compiling:- pre-evaluating fn:collection("Collection")- simplifying descendant-or-self step(s)Query:for $x in collection('Collection') return $x//PoetSessionOptimized Query:for $x_0 in (db:open-pre("Collection",0), db:open-pre("Collection",766), ...) return $x_0/descendant::PoetSessionQuery plan:<QueryPlan> <GFLWOR> <For> <Var name="$x" id="0"/> <DBNodeSeq size="103"> <DBNode name="Collection" pre="0"/> <DBNode name="Collection" pre="766"/> <DBNode name="Collection" pre="1242"/> <DBNode name="Collection" pre="2008"/> <DBNode name="Collection" pre="2777"/> </DBNodeSeq> </For> <IterPath> <VarRef> <Var name="$x" id="0"/> </VarRef> <IterStep axis="descendant" test="PoetSession"/> </IterPath> </GFLWOR></QueryPlan>