18. The system of claim 13 , wherein the query result instructions include selecting instructions for selecting entries in the query result table that satisfy a predefined criterion.
18. The system of claim 13 , wherein the query result instructions include selecting instructions for selecting entries in the query result table that satisfy a predefined criterion. 20. The system of claim 18 , wherein the predefined criterion is satisfied if a selected entry in the query result table is among a group of entries having highest numbers of session identifiers in the query result table.