Using the following knowledge:

Disease D$1$ has Symptoms S$1,$ S$2,$ S$3$

Disease D$2$ has Symptoms S$5,$ S$6$

Disease D$3$ has Symptoms S$1,$ S$4,$S$3$

Disease D$4$ has Symptoms S$5,$ S$2,$ S$7$

Disease D$5$ has Symptoms S$1,$ S$3,$ S$8$

Disease D$6$ has Symptoms S$5,$ S$3,$ S$8$

Disease D$7$ has Symptoms S$5,$ S$9,$ S$8$

Where D$1,$ D$3,$ and D$5$ belong to class C$1$

D$2$ and D$4$ belong to class C$2$

D$6$ and D$7$ belong to class C$3$

Devise an appropriate knowledge representation scheme to be used by the Hierarchical Classification Generic Task for diagnosis where the nodes of the hierarchy must be classes or disease.