How can I count the number of facts of a partilcuar type inserted into the rules session?

lets say, I insert several instances of fact called Asset into the rules session.

I need to write a web guided decision table that outputs a specifc text value in an action column based on the number of assets in memory.

numberofAssets      result

1                            result1

2                            result2

3                            result3

How can I create a condition column that counts the number of Assets in memory ?

question2:

If I want to write a drl  that needs to count number of Assets in memory and print that value, can I use a collect from or is it only used with a Collection ?

As always ,

 Thank You all for your fast responses and ideas.

Thanks,

Ram