A baseline is a version of a document tied to a particular project stage, to a release, or to an iteration. Baselines are displayed in the project plan. This makes it possible to check that documentation current for the given stage is present, and to use it for day-to-day work. You can compare arbitrary document baselines with each other to identify differences. Using the "Text as of Date" filter, you can obtain exactly the requirement text that corresponds to the specified date.
Create baselines of operational documents before making the changes that arise from enhancements in a new product version. This lets you keep the description of the functionality of previous versions. You can easily export the documentation for the required version, or automate this process in order to embed the documentation in the product.
If you need to make changes to several product versions at once, or to documentation partially adapted for different customers (or for different languages and localization), use documentation branching.
Baselines can be used as additional documentation branches, thus implementing documentation branching by analogy with source code branches. This allows documentation for several versions of the same product to be developed in parallel.
ALM automatically suggests which changes from the main documentation baseline need to be carried over into the other documentation branches.