Table 1 Symbols

\( {\text{se}}_{si} \)

Score of learner s on learning object \( i \)

\( \overline{\text{se}}_{i} \)

Average score of learner l

\( q\left( {i,d_{1} } \right) \)

Prerequisite correlation coefficient between learning objects i and d₁

d₁

First unqualified learning object

d₂

Last qualified learning object

\( {\text{dis}}_{{si, sd_{1} }} \)

Time distance between 2 learning behaviors of learner s on learning objects i and d_1.

I_pr

Learning object set for prerequisite recommendation

I_fr

Learning object set for subsequent recommendation

sim_sr

Similarity between learner s and r

p_ri

Recommendation value of learning object i for learner r