This is probably the last post in this series. I will try in this article to bring it all together. This will also be the most code heavy article. If you are new to migrate and Drupal-to-Drupal data migration, make sure you read and understand the first articles before preceding.
Mapping fields (field mappings)
Migrate have no way of knowing your plans for your Drupal 6 CCK fields or to what fields you are planning to store the data in Drupal 7. Perhaps you do not want or need to migrate all your old data. Source and target field have the same field name and type, but sometime you might want to fix a bad decisions made in the past and reorganize your architecture. Migrate call this field mappings. What ever reason you might have, you will need to share these ideas with Mirate. The basic format is like this:
More details are found in the official documentation at drupal.org.
An example of this is found in article.inc:
This map field_foo (drupal 6) to the cleverly named field field_bar (drupal 7). This is all it take to get a text field like this migrated if you re-run the node migration drush mi Article.