flowchart LR
%% element use
T --> C1 --> C11 --> O111
%% element definition
E([ exp ])
C([ com ])
T([ the ])
C1(( QM ))
C11(( MNDO ))
O111[\ DR1 \]
C2(( MD ))
C3(( FD ))
C4(( SVFE ))
%% class use
class E approach
class C approach
class T approach
class C1 topic
class C11 topic
class O111 output
%% class style definition
classDef approach fill:#afa,stroke:#3a3,stroke-width:2px
classDef topic fill:#aaf,stroke:#33a,stroke-width:2px
classDef output fill:#faa,stroke:#a33,stroke-width:2px