You must prepend a metatag name with "e." to specify the current event or with "w." to specify the past events
All window simple Boolean expressions must include a metatag in the form w.[metatag].
For more information about valid filter expressions, see Filter Operation.
Every event coming in to the Correlation Engine that passes this filter is put into the window of past events
If no filter expression exists, then all events coming into the Correlation Engine are maintained by the window. With extremely high event rates or long durations, this may require a large amount of memory.
The current event is not placed into the window until after the current event window evaluation is complete
To minimize memory usage, only the relevant parts of the past events, not all metatag values, are maintained in memory.