OML

OML (Outline Markup Language) is an XML format for outlines. It was originally proposed by Ray Grieselhuber. The specification is designed to build upon the concepts found in OPML, with the goal of fixing some of its limitations.

OML has a structure similar to OPML. Its advocates claim that although it is as simple and as flexible as OPML, its extension mechanism is better than that of OPML. Instead of letting users add attributes freely, OML introduces an <item> element (child element of <outline>); instances of the <item> element may be added freely.