RCOMM 2012 Sudoku Challenge: 3 - Drop impossible values (loop)

Process from the http://rcomm2012.org live data mining challenge. The task was to partially solve a Sudoku puzzle by solving three subtasks. Processes 1-3 in this pack are the actual solutions to the tasks, process 0 loads the required data into your repository and process 4 is the bonus that solves the entire puzzle.

IMPORTANT: Save this process as "RCOMM 2012 Sudoku Challenge: 3 - Drop impossible values (loop)" since it is included from process 4. This process uses process 2 repeatedly to eliminate values that can be excluded by looking at all entries in "Sudoku Predefined". Therefore it iterates over "Sudoku Predefined" each time selecting one to be processed by process 2. A combination of Remember and Recall is used to feed the data set containing the remaining possibilities - starting with "All Possibilities" into the subprocess. Once only possible combinations remain, we are interested in those cells where there is only one possibiliy left. This is achieved by an Aggregate operator. Finally we append the newly generated knowledge (those cell values that are certain) to those which were predefined.