1. A keyword is a focused word that describes the book or a post.
2. Keywords define the content and are what people are searching - https://www.editeur.org/files/ONIX for books - code lists/ONIX_BookProduct_Codelists_Issue_34_Changes.pdf e.g.:
3. Keywords should use the <b067> (<SubjectSchemeIdentifier>) Onix field, and the correct value for keywords is 20.
4. Each keyword should be added to <b070> (<SubjectHeadingText>) separated by semi-colon.
Keyword value 20 is important here as there are other fields that can be added to <b067> that mean something different, e.g: https://home.bic-media.com/onix_info/2-1-4/codelists/onix-codelist-27.htm