Table 1 Inference rules

A node of minimum level is followed by another node of minimum level or medium level.

Node(?n1) ˄ Node(?n2) ˄ next(?n1,? n2) ^ belongsTo(?n1, “minimum”)

→ (belongsTo(?n2, “minimum”) ˅ belongsTo(?n2, “medium”))

The educational resources that are part of a node of minimum level must have low difficulty^a associated.

Node(?n1) ˄ Content(?c) ˄hasContent(?n1,?c) ˄belongsTo(?n1, “minimum”)

→ ((describedBy(?c, “easy”) ˅ describedBy(?c, “very easy”))