before selects those values for an attribute before some identified position.
For example, given the following case fragment,
13 Feb 03 03 Oct 03 16 Nov 03 20 Dec 03 ABC 2.5 3.2* 2.9 2.7 GHF t t f f
at least 1 ABC before GHI is “f” is high
at least 1 ABC before ABC is high is normal