Zettel ID and General Unique Identifiers
The notion of Zettel ID as a Unique Identifier can also be expanded to a more broad system that encompasses more than your Zettel notes. In my personal system, any object can have a GUID (General Unique Identifier) - Zettels, books, paper documents, even To-Dos or (digital/analog) calendar events - your imagination is the limit.
This GUID works across all application and media boundaries to reference one object to another, just like Zettel IDs. In principle, you could use time-unique stamps, but those are clunky to use in any context where you can't copy-paste (such as in paper notebooks or when there's a physical separation of devices). As such, I personally construct the GUID much differently from a typical note ID (see further down)
Let me show you an example: My notes on Stephen Covey's book "the 7 habits of highly effective people" ( I use evernote for all my needs; sorry for it being in German):
It contains a link to my to-do manager (denoted by the "T" at the GUID start. Let's look for that:
Which again includes GUIDs that have been copy-pasted.
Because they're so short, the GUID also works with hand-written notes. You can also include things like page numbers:
A few notes on the GUIDs:
First of all, the system in place is something that works for me - they originally came into being in high school as a way to link various sources and homework, etc. I would write for example write HA-M-150106-1|12-16,18b (Hausaufgabenblatt (exercise sheet), mathematics, 15. January 2006, sheet number one, problems 12 to 16 and 18b) so that I knew what I needed to do for homework and don't confuse sheet problems 12 to 16 with sheet 3 problems 12 to 16 that we got that week. From the beginning, this system included a key of what topic the referenced object was about and what the object actually was (homework sheet, book page, a digital file, etc.). This way of doing things stuck with me.
Secondly: The main difference of ZIDs and my GUID system is that the GUID system includes information about the type of object referenced (or, where to find it - [EN] for Evernote [T] for Task manager, [K] for calendar (Kalender), etc.) and a way of including the contents of the object (topic, page number, etc).
I soon expanded the system to find my way in longer documents. You can see it in the 3th example image, on the bottom and top: Use [GUID|#'$] to mark page numbers (#) and smaller units ($, for example sections, or numbered annotations). To jump inside a document, I use just [Page number] or [Page number|annotation number]. Works with e-books, as well. Something similar for references in Zettelkasten, with [A], [B], etc. linking sources with individual sentences:
You can of course use increasing numbers or a date-number of item format for your Zettelkasten: [ZK-190525-3] would be the 3th Zettel Note today; or somthing like [ZK-M-0007a3a] - Zettel about Mathematics, overarching #0007 (set theory), a3a (Cantor's theorem) - you see you can easily construct either hierarchy, Folgezettel or both with it.
I won't claim that this system is the best one for standalone Zettelkastening (?) - it was, after all, there before the Zettelkasten and as such, the ZK had to fit the existing system. However, it has a few advantages against using time stamps as IDs, such as universality, supporting hierarchy/Folgezettel (if you use that) and the fact that you can see what the object you're touching is about. I just wanted to put it out here to hear your thoughts and maybe serve as an inspiration.
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