You can build mapplets in the Mapplet Designer when you want to use a standardized set of transformation logic in several mappings. When you use a mapplet in a mapping, the Designer creates an instance of the mapplet. The mapplet instance displays only the ports from the Input and Output transformations. These transformations display as groups. You can enter comments for the instance of the mapplet in the mapping, but you cannot edit other mapplet properties.
You can expand the mapplet in the Mapping Designer by selecting it and clicking Mappings > Expand from the menu. This expands the mapplet within the mapping for view. You can open or iconize all the transformations in the mapplet and mapping, but you cannot edit any of the properties.
When you edit the mapplet in the Mapplet Designer, all instances of the mapplet in mappings inherit the changes. Some changes might invalidate the mappings using the mapplet.