LMNL (the Layered Markup and Annotation Language […]) overcomes the limitations of marking up non-hierarchies in XML, except that it steps entirely outside the XML paradigm to do so. It can represent unlimited overlap of all kinds. In principle LMNL is a data model, not a syntax with an implied data model as SGML was, and as XML was until DOM and the Infoset added models. LMNL does provide a syntax, which is similar to MECS in that it does not require pure nesting like well-formed XML. Components are allowed to overlap arbitrarily, except that self-overlap requires co-indexing (as seems inherantly [sic] necessary for a flat syntax to support structures such as overlap and DAGs, that unlike trees cannot be traversed with merely a stack).