Mapplets and Transformation

Here I continue to write about Informatica.
Mapplet and Transformation are two important things that you will use a lot while developing your mappings.

What Exactly is Mapplet
A mapplet is reusable component of mapping.Suppose you feel that you are going to change date to '10/10/2009' whatver date may come for all the tables.
For loading data into different tables you will have differnt mapping.
You can create a mapplet for such purpose.
You can drag this mapplet than to mapping.
Mapplet will contain various transformation like expression,filter,lookup
A mapplet will have input as well ouput.
When you drag a mapplet to mapping you will connect one of its port to input and other to output.

Expression
To perform various operation in informatica you need to have transformation.Transformation can be of several type like expression,filter(Each transformation will be covered in detail).
Transformation can be of two
1. Active : They change the number of rows passing through them like filter
2. Passive : They dont change the number of rows passing throught them like expression.
I know some of you may not be getting what I write.
Please share your view and let me know on which topic I can expand more.
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