The content of some classes of document, for example dictionaries or lexical knowledge bases, can greatly benefit from compact representation using inheritance hierarchies. However current approaches to document markup do not provide mechanisms to support such representations. This paper proposes such a mechanism, introducing markup and associated semantic operations to support the annotation of inheritance structure in document content. The proposal is grounded in the markup language XML (but in the talk I will only assume familiarity with HTML), and inheritance examples are in the lexical description language DATR. With luck and a fair wind, the presentation will include a demonstration of a web server for HTML pages with embedded DATR definitions.