Mapping Methods

Taxonomy mapping provides a way to establish a correspondence between elements in a source taxonomy and elements in a target taxonomy.

There are these different methods to map elements in CDM XBRL:

• Using the element ID
• Using local names
• Manually mapping elements

If an element uses the same element ID or local name in both taxonomies, those elements are mapped together by CDM XBRL when you select the element ID or local name option.

Tip: To override any of these mappings, select the element and provide a new mapping.

Any elements that cannot be mapped by CDM XBRL can be manually mapped in the Add Taxonomy Mappings window.

The Add Taxonomy Mappings window has these columns: Map from Taxonomy and Map to Taxonomy. You can load your current taxonomy as the Map from Taxonomy and the new taxonomy as the Map to Taxonomy.

The following list contains mapping types along with the implications they have during taxonomy replacement:

• Replacement
  A replacement maps an element in the Map from Taxonomy to another element in the Map to Taxonomy. A replacement mapping can be considered a one-to-one mapping. A replacement mapping causes the taxonomy replacement feature to remap a tagged element to the new element in the Map from Taxonomy.

  Important: A tag replacement might fail because of dimensional incompatibilities between the dimensional structures in the elements. This mapping would result in the removal of that tag.

• Ignore
  This option ignores all tags that are associated with the selected element during a taxonomy replacement. This results in the removal of ignored tags.
• Merge
  Merging elements maps more than one element in the Map from Taxonomy to a single element in the Map to Taxonomy. A merged mapping can be considered a many-to-one mapping. You might merge elements if an element in the Map from Taxonomy was replaced by a single element in the Map to Taxonomy. For example, the expense_Pencil and expense_Pen elements are replaced by the expense_Writing_Tools element. This mapping would result in the removal of tags from the Map from Taxonomy element during a taxonomy replacement.
• Split
  Splitting maps a single element in the Map from Taxonomy to multiple elements in the Map to Taxonomy. Split mappings can be considered a one-to-many mapping. You might split an element if that element in the Map from Taxonomy was replaced by multiple elements in the Map to Taxonomy. For example, the expense_Buildings element is replaced by expense_Warehouses and expense_Factories elements. This mapping would result in the removal of the tag from the Map from Taxonomy element during a taxonomy replacement.

After you map elements, you can use the taxonomy replacement feature to switch to a new taxonomy. When a Map to Taxonomy is used with a tagged report, CDM XBRL updates the tags with the mapped elements in the Map from Taxonomy.

When two taxonomies are loaded into the Add Taxonomy Mappings window, you can use the element ID or the element local name to determine the method for mapping the elements. You must be familiar with how the taxonomy was created to select the better method.

If you know that the element IDs are the same in the two different versions of the taxonomy you are mapping, you can use this method. If you know that the local names are the same, use the local name option. Generally, you would select the method that would result in more elements mapped automatically by CDM XBRL. However, you can select either method as appropriate. For either method, if the element IDs or local names are changed, fewer elements are automatically mapped.

If you use the element ID method, CDM XBRL searches the two taxonomies for the ID for each element, and maps elements that are based on that ID. Any elements with IDs that are the same in both taxonomies are automatically mapped together.

If you use the local name method, CDM XBRL searches the two taxonomies for the namespace:localname string for each element, and maps elements that are based on the local name part of the string. Any elements with local names that are the same in both taxonomies are automatically mapped together.

Bidirectional Mapping

Bidirectional mapping is mapping in XBRL in which the element in either taxonomy can be considered the source element. Bidirectional mappings can be used if you have an XBRL project that is associated with multiple reports, such as a quarterly report and an annual report.

For example, you might map Element_A in the quarterly taxonomy to Element_B in the annual taxonomy. If you load the quarterly taxonomy, and tag a value as Element_A, when you load the annual taxonomy, that tag becomes Element_B. If you again load the quarterly, the tag reverts to Element_A.

If you create a bidirectional split between Element_A in one taxonomy with Element_B and Element_C in the other, the split becomes a merge of Element_B and Element_C to Element_A.