An excellent way to implement labels and contexts for cross-correlating information is to assign tags to headlines. Org-mode has extensive support for tags.
Every headline can contain
a list of tags; they occur at the end of the headline. Tags are
normal words containing letters, numbers,
‘_’, and
‘@’. Tags must
be preceded and followed by a single colon, e.g.,
‘:work:’.
Several tags can be specified, as in ‘:work:urgent:’. Tags will by default
be in bold face with the same color as the headline. You may
specify special faces for specific tags using the variable
org-tag-faces, in much the same way as you can for
TODO keywords (see Faces for
TODO keywords).