For those of you wondering what relations are and how to use them: In BibSonomy, a relation consists of two tags, SUBTAG -> SUPERTAG. On the relations-page you'll find e. g. the following relation: 'algebra' -> 'mathematics'. It means that 'mathematics' is the supertag (also called a concept) of 'algebra', and the relation could be read as 'algebra is a subdiscipline of mathematics'.

You can define and manage your own relations on the edit_tags-page. Or you can enter a relation in the tag field while posting or editing a bookmark/publication. Just use SUBTAG->SUPERTAG (without any white space) as a tag.