For example, you might create an Expression transformation that calculates value-added tax for sales in Canada to analyze the cost of doing business in that country. Rather than perform the same work every time, you can create a reusable transformation. When you need to incorporate this transformation into a mapping, you add an instance of it to the mapping. If you change the definition of the transformation, all instances of it inherit the changes.

The Developer tool stores each reusable transformation as metadata separate from any mapping or mapplet that uses the transformation. It stores reusable transformations in a project or folder.

When you add instances of a reusable transformation to mappings, changes you make to the transformation might invalidate the mapping or generate unexpected data.