Using InDesign, you can include comments and processing instructions in an XML file. Enter a comment to include descriptive information about an element. Comments can be viewed in web browsers and text editors. They help others understand XML structure and XML tags. A processing instruction is a special, application-specific command. For example, you can enter a page-break processing instruction so that an application to which you export your XML file understands where to enter a page break. InDesign user-created processing instructions are meant for use in other programs; InDesign itself does not act on processing instructions.
Comments and processing instructions appear in the Structure pane. You can move, edit, and delete comments and processing instructions as you can other elements in the Structure pane. They cannot, however, contain child elements or attributes.