Once found, the plan must be transformed to reality. This can be achieved by the compile method of Path. The product is an object of the Mill interface.

The Mill is the real filter (or series of filters) that can transform "something" (A) to "something" (B). For this, we must enter the input "something" - the object (A). This is done by calling the initialize method. This, however, is only sufficient in the simplest of cases. More often, we must also send some initial input to all participating (elementary) filters which were represented by the original Edges. Moreover, these filters can extract secondary data during the filtering, which can be collected with the harvest method. The initialization of elementary filters is provided by the sow method. Both methods operate over a Hashtable, where the initial objects for/from the parsers are stored.

	Tip
	If you call initialize with a null, it resets the Mill and you can use it again and again. On the other hand, this feature must be supported by you when you add your filters to the system (see below).