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+|reclass| is an "external node classifier" (ENC) as can be used with
+automation tools, such as `Puppet`_, `Salt`_, and `Ansible`_. It is also
+a stand-alone tool for merging data sources recursively.
+
+The purpose of an ENC is to allow a system administrator to maintain an
+inventory of nodes to be managed, completely separately from the configuration
+of the automation tool. Usually, the external node classifier completely
+replaces the tool-specific inventory (such as ``site.pp`` for Puppet,
+``ext_pillar``/``master_tops`` for Salt, or ``/etc/ansible/hosts``).
+
+With respect to the configuration management tool, the ENC then fulfills two
+jobs:
+
+- it provides information about groups of nodes and group memberships
+- it gives access to node-specific information, such as variables
+
+|reclass| allows you to define your nodes through class inheritance, while
+always able to override details further up the tree (i.e. in more specific
+nodes). Think of classes as feature sets, as commonalities between nodes, or
+as tags. Add to that the ability to nest classes (multiple inheritance is
+allowed, well-defined, and encouraged), and you can assemble your
+infrastructure from smaller bits, eliminating duplication and exposing all
+important parameters to a single location, logically organised. And if that
+isn't enough, |reclass| lets you reference other parameters in the very
+hierarchy you are currently assembling.