Elements, element entities, and attribute entities (which together are called “artifacts”) contain Comments and Processing Instructions in both their Definition tab and their Instance tab. Text entered into these properties within the Definition tab is generated to the place in the schema where the artifact is declared and defined. Text entered into these properties within the Instance tab is generated to the place in the schema where the artifact is used.

For example, if, in a diagram, Element_3 contains Element_1, a comment within the Instance tab of Element_1 will generate directly above the occurrence of Element_1 in the DTD (not where it is declared):

A comment within the Definition tab of Element_1 will generate directly above the place in the DTD where Element_1 is defined/declared:

For example, if, in a diagram, Element_3 contains Element_1, a comment within the Instance tab of Element_1 will generate directly below the occurrence of Element_1 in the schema: