Michael Andrews literally wrote the book on metadata for web content (actually two books).

Metadata puts the structure in structured content. It helps both humans and computers understand what your content is about and how it relates to other content. It ensures that your content is always up to date, easy to find, and able to be tailored to your customers' unique needs.

In today's hyper-connected and ever-evolving digital media landscape, every online publisher needs a content metadata strategy.

https://ellessmedia.com/csi/michael-andrews/