A radically simpler way to markup documents.
Cobalt is a follow up on Hope. It is a very simple implementation of Ted Nelson's 'Edit Decision List' concept for markup.
Cobalt is a research implementation, to explore this concept better. But Hope has found its way into production code. It is the engine of change in SimplyEdit. This is because the browser API for contentEditable (the WYSIWYG editor built into almost all browsers) is pretty useless. If you want to implement your own replacement for the execCommand API, you'll need to apply the change to the DOM yourself. This is not trivial. With a good 1 to 1 translation from html to Hope and back, applying changes to the DOM do become trivial.
There are many subtle issues with the way markup in general and HTML in particular works. But the most important issue is about editing. HTML was designed to be written in a text editor, not in a What-You-See-Is-What-You-Get (WYSIWYG) editor.
So to be able to see which part of a text has which markup applied to it, the natural solution is to wrap
that part in a start and end tag. To see which start tag is ended by the end tag, the end tag re-states the tag
name. So you get markup like this: <em>italic text</em>.
To add an extra layer of markup, you add another start and end tag. But these tags may not overlap. You cannot
do this: <em>italic and <strong>bold</em> text</strong>. Instead you do this:
<em>italic and <strong>bold</strong></em><strong> text</strong>.
In effect you are building a tree structure. When this tree structure gets a bit more complex, it becomes difficult to follow in a text editor, unless you indent the markup. Each level of markup is indented, so the tree becomes visible. But this adds extra whitespace and linefeeds, that are only there to allow you to indent the markup.
I've been working on Hope and later Cobalt for quite some time, so what have I learned so far?