The primary problem I see with this is that XML content is fundamentally text, not bytes. Using your types, two XML documents with identical content but different encodings will have different Haskell values (and thus be incorrect regarding Eq, Ord, etc). Additionally, since the original bytestring is shared in your types, potentially very large buffers could be locked in memory due to references held by only a small portion of the document. Chopping a document up into events or nodes creates some overhead due to the extra pointers, but allows unneeded portions to be freed. If you'd like memory-efficient text storage, using Bryan O'Sullivan's "text" package[1] is probably the best option. It uses packed Word16 buffers to store text as UTF-16. Probably not as efficient as a type backed by UTF-8, but it's much much better than String. I know the data types you specified are just examples, but they're leaving out some important XML features -- namespaces, entity references, etc. Consider either reading the XML spec, or perhaps use my package "xml-types"[2] as a starting point for designing your type hierarchy. [1] http://hackage.haskell.org/package/text [2] http://hackage.haskell.org/package/xml-types