The "d" tag appears to be a "topic" tag, not a "title" tag. That's why this is confusing. They apparently have their users select a wiki topic and if they later change the text displayed at the top, that is saved as a title.
That is not transparent.
Discussion
That doesn't really transfer to books, as books have actual, official titles, but I could imagine some sort of category.
So, the d tag for a book might just be "Bible", but the title would be "Douay-Rheims Catholic Bible".
Or "literature" and "Tale of Two Cities"
That’s what the “title” tag is for. The d tag is just a unique identifier. Some people use random values, some people use a timestamp, or you can use a derivation of the human-readable title understanding it can’t be changed and must be unique
Okay, then "d" tag is just an identifying string. Then we need to figure out a pattern for that, that other clients might be able to emulate. That's traditionally ISBN, but we won't always have those.
Maybe some sort of hash.
You can do whatever as long as it’s unique. I normalize the title and add a random value at the end
“This is a title” turned into “this-is-a-title-6775466”
From then the title tag can change but the d tag must remain the same
I didn't realize that you add that number. All I see in the raw json is "this-is-a-title". 🤷♀️
So I assumed that it's a subject, not an ID.
That's why I've been writing simple things like "john-1", to denote "The First Book of John from the New Testament Bible", so that all of the entries can be found and line up under each other, on Wikifreedia. Since there will eventually be 20+ "john-1" entries for the different Bible editions.
I mean, really we could go whole-hog and include things like ISBN number, publisher, language group, etc.