I have sent the following message to Haskell-Cafe five days ago; it seems to have disappeared. I'm resending because HSXML answers your second question, of ensuring complex content constraints. I'm not sure why do you need Monad specifically? HSXML documents are particular monoids, which is what we want from documents. Generally speaking, all we need is a way to create primitive documents and to compose them into bigger ones. There are many more composition operations than monadic bind. Not everything is a monad and not everything has to be a monad. Old message: Somewhat related is the HSXML library for generating valid XML and HTML. To be precise, the library is designed to express in the type system content model constraints such as: block-level elements like DIV are allowed only in the block-level context; one cannot put DIV within H1, for example. Some items may be polymorphic: for example, TITLE appears in HEAD, it can be an attribute and it can be an element. It can be rendered differently in each case. The same HSXML document may be rendered as HTML or XML (or something else entirely, e.g., PDF). http://okmij.org/ftp/Scheme/xml.html#typed-SXML