If you’ve been around the Emacs technical community for a while, you know that Sacha Chua—despite being the mother of a young daughter—is an ever present and incredibly productive member of that community. One of the ways she manages that is by automating as much of her work as she can.
In a recent post she shows one such bit of automation. As almost every Org mode user knows, you can add executable code blocks to an Org file that can be executed to perform various actions, usually—but not always—altering the text of the Org file in some way. In the example that Chua gives, calendar entries are parsed and used to build crontab entries to perform certain actions in a timely manner. Chua gives the details here.
You can check out her code at the post but the aspect I want to focus on is her use of Property ID for an Org subtree. For her purposes, the ID can be used to execute every code block In the subtree. That means that she can mix various languages to build her crontab entry but execute them all with a single call to build the entry. That’s pretty neat.
The other, perhaps more useful, thing you can do with a Property ID is set an anchor point for the subtree if you export it to HTML. For example if you have a document with several subtrees—a blog post, say—that you want to publish to the Web you can have any or all of those subtrees directly addressable through a URL because the Property ID sets an anchor point for the subtree. That’s a really handy thing to know.