And then there is https://schema.org/
It's the item* attributes, e.g.: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/...
Also Dublin Core in <meta> tags.
Why do they keep adding conflicting meta data formats to HTML!?!
For example, there's no explicit property in schema's Person type [1] for a nickname. But the FOAF standard does [2].
Just add FOAF to the JSON-LD context:
{
"@context": {
"@vocab": "https://schema.org/",
"foaf": "http://xmlns.com/foaf/0.1/",
"pronouns": "https://schema.org/pronouns"
}
"@type": "Person",
"givenName": "Timothy",
"familyName": "Berners-Lee",
"foaf:nick": "TBL",
I think you should just think about what metadata you actually care about, and the main metadata I care about (choose your own list) is authorship, publish date, last update, subject keywords, thumbnail (OpenGraph 1200x630), and summary.
There’s a long list of additional metadata that I could put in my webpages because there are standardized ways to do it, but, why bother?
And yes, you should use whatever metadata is applicable to your site and test it against the search engines/etc. you want to support to make sure that they are reading the metadata correctly.
Json-ld says: if you want to know whether the “title” property means the schema.org or the dublin core variant then you can find out which it is by <json-ld algorithm>
So you’d always use json-ld _with_ schema.org or something.