They relate aboutness directly to recall and precision measures.
Articles on aboutness continue to appear in the literature. Hjørland (2001) and Bruza et al. (2000) are examples. While these may have some academic interest (Hjørland goes to great length to try to distinguish such terms as “subject,” “topic,” “theme,” “domain,” “field,” and “content”), they have no practical value to the indexer who would do well to ignore such semantic differences and simply give an item the labels that will make it usefully retrievable by members of a target community.