Esper EPL pattern fires only once

I am trying to create a pattern in EPL, but i do not get why it gets matched only one. Here is what I did on the web page Esper EPL online. The EPL I input in the left textbox is:

create schema StockTick(signature string, source string, destination string, action string);
@Name('Monitor') select * from StockTick;
@Name('Out') select * from pattern [A=StockTick -> B=StockTick(B.source = A.source and B.destination = A.destination and B.action='block') where timer:within(2 seconds)];

and the events I input in the middle textbox are:

StockTick={signature='sig1', source ='s1', destination ='d1'}
t=t.plus(0.4 seconds)

StockTick={source ='s1', destination ='d1', action='block'}
t=t.plus(0.4 seconds)

StockTick={signature='sig2', source ='s2', destination ='d2'}
t=t.plus(0.4 seconds)

StockTick={source ='s2', destination ='d2', action='block'}
t=t.plus(0.4 seconds)

The output I get in the right box:

At: 2001-01-01 08:00:00.000
Statement: Monitor
Insert
StockTick={signature='sig1', source='s1', destination='d1', action=(null)}

At: 2001-01-01 08:00:00.400
Statement: Monitor
Insert
StockTick={signature=(null), source='s1', destination='d1', action='block'}
Statement: Out
Insert
stmt2_pat_0_1={A={StockTick={signature='sig1', source='s1', destination='d1', action=(null)}}, B={StockTick={signature=(null), source='s1', destination='d1', action='block'}}}

At: 2001-01-01 08:00:00.800
Statement: Monitor
Insert
StockTick={signature='sig2', source='s2', destination='d2', action=(null)}
At: 2001-01-01 08:00:01.200
Statement: Monitor
Insert
StockTick={signature=(null), source='s2', destination='d2', action='block'}

So:

after 0 seconds, the Monitor statement gets fired (fine!)
after 0.4 seconds, the Monitor statement gets fired again (fine!)
after 0.4 seconds, the Out statement gets fired (fine!)
after 0.8 seconds, the Monitor statement gets fired again (fine!)
after 1.2 seconds, the Monitor statement gets fired again (fine!)

What I do not understand is why after 1.2 seconds I do not get fired the Out statement again, as I would expect.

Please note that if I try the first two inserts alone and the second two inserts alone, in both cases I have the Monitor statement fired twice and the Out statement fired once. The problem arises when I concatenate the four insert statements.

Solution

Thanks to another forum, I managed to solve the problem. I missed the every keyword in defining the pattern, so, after updating the rule as follows:

@Name('Out') select * from pattern [every A=StockTick -> B=StockTick(B.source = A.source and B.destination = A.destination and B.action='block')];

it worked like a charm:

At: 2001-01-01 08:00:00.000
Statement: Monitor
Insert
StockTick={signature='sig1', source='s1', destination='d1', action=(null)}

At: 2001-01-01 08:00:00.400
Statement: Monitor
Insert
StockTick={signature=(null), source='s1', destination='d1', action='block'}
Statement: Out
Insert
stmt2_pat_0_0={A={StockTick={signature='sig1', source='s1', destination='d1', action=(null)}}, B={StockTick={signature=(null), source='s1', destination='d1', action='block'}}}

At: 2001-01-01 08:00:00.800
Statement: Monitor
Insert
StockTick={signature='sig2', source='s2', destination='d2', action=(null)}

At: 2001-01-01 08:00:01.200
Statement: Monitor
Insert
StockTick={signature=(null), source='s2', destination='d2', action='block'}
Statement: Out
Insert
stmt2_pat_0_0={A={StockTick={signature='sig2', source='s2', destination='d2', action=(null)}}, B={StockTick={signature=(null), source='s2', destination='d2', action='block'}}}