I am going to dumb things now, so if someone has an issue with my explanation, just be aware that I am trying to simplify some of the concepts; and that I am not that knowledgeable in the history of the whole URL, but I am speaking from what I know.
In a few words URL Schemes are based on the idea of using text based links to open an application or applications and execute a set of instructions.
For example, there is the web URL Scheme that starts with “http://” and then it gives you an address. When you click on that address, the program in your system registered to handle that scheme (Safari, Firefox, Chrome, etc.) opens and takes you to where you want to go. This was popularized with the early advent of the internet and some of the services that made use of schemes like,
“ftp://”
“mailto:”
“smb://”
Later on, Apple implemented a way for developers to create their own scheme so that other applications could interact with others without creating complex bridge code or opening themselves to certain attacks. Imagine Object Oriented programing with the passing of instructions being done by the operating system itself.
For the examples, well…
Imagine opening a text file and including an URL like “http://taskpaper.com”. Now, when you click on that link, your computer opens a browser and takes you to that place. Or writing something like “mailto:billgates@microsoft.com” and when you click on it, your computer opens up your default email app and starts a new email to…
Apple makes use of these Schemes on their apps, to open preference panels. Go to a certain place in the iOS settings, etc.
Hopefully this helps you understand my previous post and the ideas I had. Also, read the implementation that Things had.
By the way… Have you tried OmniOutliner? It has all of the formatting that you want done in your lists. Hope that this helps. Have a good one!