An alternative (or conditional) node is a group of objects, one or none of which will be applicable and thus displayed in a given situation.The following discussion of the element <dmNodeAlts> applies to any other alternates group such as:The alternates group concept is detailed in Chap 4.13.3.The element <dmNodeAlts> (a group of node alternatives) provides the ability to group occurrences of the element <dmNode> together which apply in different contextual situations. Only one node or none of the group will be displayed. For example, three versions of a "disconnect connector" step can exist in the element <dmNodeAlts> due to equipment configuration differences. For any configuration, only one version of the step applies. The logic engine will evaluate the applicability expression for all occurrences of the element <dmNode> within the element <dmNodeAlts>. Only the first node whose applicability expression evaluates to TRUE will be displayed. There need not be an occurrence of the element <dmNode> within the element <dmNodeAlts> that is applicable to every possible situation. In such cases, the logic engine simply moves on to the next element <dmNode>. Every node in an alternative node must have applicability. Applicability on the alternative elements is optional in the content section of the Schema with the exception of the element <dmSeqAlts> within the element <dmIf>. For alternative processing, however, applicability is required on the alternative elements.Applicability on the nodes of an alternates group must be mutually exclusive. Although the Schema does not require the alternative element <dmNode> to have mutually exclusive applicability (or the attribute applicRefId at all), it is important to understand the danger of overlapping applicability on alternative nodes. At most one will pass thru the logic engine to be displayed to the user, and if more than one applies, the user will miss something. A node with no applicability always applies. There can be reasons to author overlapping applicability within an alternates group, but it is not recommended.