Hierarchical / multilevel vocabularies

[pdpinch]

As a curator, I would like to have hierarchical or multilevel vocabularies, particularly for assigning learning objectives. A course may have hundreds of learning objectives and it is difficult to navigate the list without some sort of hierarchy. Here is an example from physics:

Vectors

• Calculate the sum of vectors by adding vectors geometrically or components algebraically
• Calculate the dot product of two vectors in Cartesian or polar coordinate systems

Momentum

• Identify situations where momentum is conserved
• Use conservation of momentum in continuous mass transfer systems

Kinematics

• Use constant acceleration kinematics to compute positions and velocities as a function of time
• Integrate acceleration and velocity to obtain position from non-constant acceleration

This feature raises a number of questions, about search UI, vocabulary UI, the vocabulary model and the search index.