[1] Using GML, a document is marked up with tags that define what the text is, in terms of paragraphs, headers, lists, tables, and so forth.
[1] The Extensible Markup Language (XML) was initially a streamlined and simplified development of SGML, but has outgrown its parent in terms of worldwide acceptance and support.
In the early 1980s, IBM developed a dedicated publishing tool called Information Structure Identification Language (ISIL) based on GML.
Panel groups can present just formatted help text to the user when pressing the help key (often F1), resemble the typical IBM i menus with embedded help texts, or complete application displays with input/output fields, and other TUI elements being formatted on screen according to IBM CUA Standards.
The overall facility is called User Interface Manager (UIM) and documented in Application Display Programming.