When you just need a difference in output, you can use DITA customization to override the default output without affecting portability or interchange, and without involving specialization.
For example, if your readers are mostly experienced users, you could concentrate on creating many summary tables, and maximizing retrievability; or if you needed to create a brand presence, you could customize the transforms to apply appropriate fonts and indent style, and include some standard graphics and copyright links.
Use customization when you need new output, with no change to the underlying semantics (you aren’t saying anything new or meaningful about the content, only its display).
OASIS DITA Architectural Specification v1.0 -- 09 May 2005
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