page name discovery is the process of starting from a URL and its HTML and coming up with a human readable name for that URL. There are many use-cases for wanting human readable text for a URL, e.g. to use as linktext when linking to it (a minimal link-preview), e.g. in response to receiving a webmention from that URL.
When you receive a webmention and want some linktext for the source link:
- use the p-name of the representative h-entry if any
- else use the p-summary of the representative h-entry if any
- else use the contents of the first
<title>element if any
- else use "Untitled", optionally appending the datetime (of when the webmention was received).
- If the name you discover via this algorithm is "too long" (by whatever constraints you have for your site/content), see comments-presentation for more details on how to handle it.
Q: What about meta tags like meta name, content, description, title etc.?
A: They're all undependable invisible metacrap. Ignore them. Using "Untitled" is safer than using likely unreliable/rotten/spammed invisible meta tags.
Q: What about meta OGP tags?
A: Same thing, just proprietary.
Q: What about Twitter Cards?
A: Same thing, but both proprietary and less open than OGP (which is at least licensed under OWFa).
Also, ignoring metacrap provides incentive to publishers to markup their *visible* content on the page, which is better for them (more reliable over time than invisible meta), and better for the consuming page (that more reliable means it's more trustworthy for the consuming page).