You create a relation extension when you want the user to receive information about other vSphere or custom objects, either in a list view or in the Object Navigator, when they select or focus on a given vSphere or custom object. For example, suppose you have created a Chassis object type which might contain one or more Host objects. You can create a relation extension for the Chassis object so that information about any related Host objects also appears in the object workspace or Object Navigator when the user selects a Chassis object.You can add a relation extension to the vSphere Web Client to create a new relationship between a given type vSphere object and any other object type in the virtual infrastructure hierarchy. If you have added a new type of object to the vSphere environment, you must create a relation extension to place your new object in the graph of vSphere objects, and to populate the Related Items views.You can also create a relation extension for two existing vSphere objects that do not have an existing relationship. You might create such a relation if you want to take advantage of the Related Items views in the Object Navigator and object workspaces for those objects, or if you have created a new object collection node for an existing object in the Object Navigator.