The basics about transformations

A Transformation is an entity made of steps linked by hops. These steps and hops build paths through which data flows: the data enters or is created in a step, the step applies some kind of Transformation to it, and finally, the data leaves that step. Therefore, it's said that a Transformation is data flow oriented. Graphically, steps are represented with small boxes, while hops are represented by directional arrows, as depicted in the following sample:

Steps and hops

A Transformation itself is neither a program nor an executable file. It is just plain XML. The Transformation contains metadata, which tells the Kettle engine what to do.

A step is a minimal unit inside a Transformation. A big set of steps is available, either out of the box or the Marketplace, as explained before. These steps are grouped in categories, as, for example, input, output, or transform. Each step is conceived to accomplish a specific function, going from a simple task as reading a parameter to normalizing a dataset.

A hop is a graphical representation of data flowing between two steps: an origin and a destination. The data that flows through that hop constitutes the output data of the origin step and the input data of the destination step.

That's enough theory for now. Let's see it in practice.