External dimensions and external taxonomies

Externally-managed taxonomies and externally-created dimensions differ in how you include them in a Developer Studio project and how Developer Studio treats them once they are part of a project.

It is important to clarify the difference between an externally-managed taxonomy and an externally-created dimension to determine which feature document is appropriate for your purposes. Use the table below to determine which one you are working with.

The following table compares an externally-managed taxonomy and an externally-created dimension:

Operation	Externally-managed taxonomy	Externally-created dimension
How do you modify or update the hierarchy after it is in the project?	Any changes to the dimension must be made in third-party tool. You then export the taxonomy from the tool, and Forge transforms the taxonomy and re-integrates the changes into your project.	You generally do not update the source file for the hierarchy after you import it into your project. If you do update the file and re-import, then any changes you made to the dimension using Developer Studio are discarded. After importing the hierarchy, you can modify a dimension just as if you created it manually using Developer Studio.
How does Developer Studio manage the hierarchy?	The third-party tool that created the file retains ownership. The dimension is almost entirely read-only in the project. You cannot add or remove dimension values from the dimension. However, you can modify whether dimension values are inert and collapsible.	After you import the file, Developer Studio takes full ownership of the dimension and its dimension values. You can modify any characteristics of the dimension and its dimension values.
How do you create the XML file?	Created using a third-party tool.	Created either directly in an XML file or created using a third-party tool.
How do you include the file in a Developer Studio project?	Read in to a pipeline using a dimension adapter with Format set to XML - Externally Managed. Forge transforms the taxonomy file in to a dimension according to the .xslt file that you specify on the Transformer tab of the dimension adapter.	By choosing Import External Dimension on the File menu. During import, Developer Studio creates internal dimensions and dimension values for each node in the file's hierarchy. If you create the file using a third-party tool and any XML transformation is necessary, you must transform the file outside the project before you choose Import External Dimension on the File menu. The file must conform to external_dimensions.dtd.