People are sitting at desks in a library.
Students cram for a test at the library
We can't infer the students are at the library to cram for a test.
exists e1 x1 x2 x3.(in(e1,x3) & n_library(x3) & at(e1,x2) & n_desk(x2) & Actor(e1,x1) & v_sit(e1) & n_people(x1))
exists e1 x1 x2 x3.(n_library(x3) & for(e1,x2) & at(x2,x3) & n_test(x2) & Actor(e1,x1) & v_cram(e1) & n_student(x1))