The use case we're exploring is the ability for writers to create and publish links to Tridion Docs Topics, but for that topic in a specific Publication. This is in the context of an web application that is getting content from Tridion Docs using DXD.

Content Manager-side

We have an approach from the Tridion Docs Content Manager perspective to link to a different Topic (in the XHTML of a given Topic) while identifying the specific Publication that the Topic should appear in (in otherprops, for example).

Content Delivery format?

But is there an appropriate (URL, TCDL, or some other) format that Dynamic Experience Delivery recognizes as a "Topic in X Publication?"

For example, with a URL like internaldocs.example.com/.../233435 from the documentation, is there an underlying format for how such a link is stored in the CD broker database? My thinking is that links to specific topics in Tridion Docs are stored as references and somewhere between the Content Manager and the Content Delivery broker database, those links are changed to a DXD-specific format, and resolved in a CD API request (over the CD Public API using graphQL, for example).  

Is it "TCDL?"

I'm looking at the Server Controls reference and see things like <PageLink>, but I'm not sure if that's specific to Tridion Sites.

Or are links to topics (in a Publication) stored as just links, as in "<a href="/986917/233435">something</a>?

Finally, over the Public Content API using graphQL queries, are there any queries or properties to get the URL of a Topic, again in a specific Publication? 

We're looking at Tridion Docs 15 specifically, seeing the CD changes and benefits that come with it. 

Update (2023-08-31): I'm continuing the investigation with my team and will report back our results. I'm realizing the answer is stored in the Broker database.. :-)