streaming window operations

[Emmanuel]

Hello,
Looking at the window operators, I see things like sum, min, max but they're 
always for a single 'field'.Is there an easy way to do stats like min, max, 
average on a window but on many different fields at once?Should I split the 
stream into many parallel streams with single fields to achieve that? it sounds 
like it would be more efficient to parse the many fields and do the stats in 
parallel within the same stream, I guess then with a customer window operator
Your thoughts on this?Thanks