As a follow up to my last email attached is Charlie McDowell's "minisample" as a Leo LP. I've omitted most of the documentation except for the code itself. You'll need a copy of Python (www.python.org) with Tcl/Tk extensions [included in win32 binary] and a copy of Leo (http://personalpages.tds.net/~edream/front.html) to open the file as an editable outline, but if you examine the file you'll see that it's just XML.

Leo opens with two panes as shown here:

The language is specified because

1. Leo has the feature of supporting "round-trip" editing of generated sources which it achieves (in this version) by embedding "sentinel comments" in generated source.
2. Language statement is used for syntax colouring code nodes.

You navigate by the nodes of the outline shown in the top left pane. Code and documentation is shown in the bottom pane. The notation used for code/documentation in Leo is pretty much that used in NOWEB. The use of an outline view is arguably not as nice as expanding and contracting a folded view in place but it is pretty intuitive once you get used to it. And as I said in my last email, the Leo default front end is essentially just a view, so presumably the UI could be changed if a folded view was preferred.

The LP community is notorious for re-inventing wheels. In my opinion, Leo, though not perfect, is the best of breed LP tool out there and its existence is worth factoring in to any new plans for the ongoing development of XML formats for LP.