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The Knowledge Flow plugin is an enterprise edition tool that allows entire data mining processes to be run as part of a Kettle (PDI) ETL transformation. There are a number of use cases for combining ETL and data mining, such as:

  • Automated Scheduled, automatic batch training/refreshing of predictive models
  • Including data mining results in reports
  • Access to data mining data pre-processing techniques in ETL transformations


If a flow definition is loaded, then the definition file will be loaded (sourced) from the disk every time that the transformation is executed. If, on the other hand, the the flow definition file is imported, it will be stored in either the transformation's XML configuration file (.ktr file) or the repository (if one is being used).

A third option is to design a new Knowledge Flow process from scratch using the embedded Knowledge Flow editor. In this case the new flow definition will be stored in the .ktr file/repository. This is the approach we will take for the purposes of demonstration.

4.2.1 Creating a Knowledge Flow Process Using the Embedded Editor

Clicking the "Show embedded KnowledgeFlow editor" button will cause a new "KnowledgeFlow" tab to appear on the dialog.


Finally, add a "TextViewer" step to the layout and connect it to the "Logistic" step by right clicking over "Logistic" and selecting "text" from the list of connections.

4.2.2 Linking the Knowledge Flow Data Mining Process to the Kettle Transformation

Now we can return to the "KnowledgeFlow file" tab in the Knowledge Flow Kettle step's configuration dialog and establish how data is to be passed in to and out of the Knowledge Flow process that we've just designed. First click the "Get changes from KnowledgeFlow editor" button. This will extract the flow from the editor and populate the drop-down boxes with applicable step and connection names. To specify that incoming data should be passed in to the Knowledge Flow process, select the "Inject data into KnowledgeFlow" checkbox and choose "KettleInject" in the "Inject step name" field. The "Inject connection name" field will be automatically filled in for you with the value "dataSet."

The choices for output include either passing the incoming data rows through to downstream Kettle steps or to pick up output from the Knowledge Flow process and pass that on instead. In this example we will do the latter by picking up output from the "TextViewer" step in the Knowledge Flow process. Note that the "SerializedModelSaver" step writes to disk and does not produce output that we can pass on inside of a Kettle transformation. Select "TextViewer" in the "Output step name" field and "text" in the "Output connection name" field. Make sure to leave "Pass rows through" unchecked.
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4.2.3 Choosing Fields and Configuring Sampling

The second tab of the Knowledge Flow Kettle plugin's configuration dialog allows you to specify which of the incoming data fields are to be passed in to the data mining process and whether or not to down sample the incoming data stream.


This tab is only applicable when data is being injected into the Knowledge Flow process.