LIMID versus UID

[MB]

How does a Limited Memory Influence Diagram differ from an Unconstrained Influence Diagram?

Is there a benefit of working with one over another?  

Thank you.

[Frank Jensen]

Limited Memory Influence Diagrams do not have a "no-forgetting" assumption.  Instead, all available information (observed chance variables and decisions) must be explicitly represented via information links.  This provides the opportunity to ignore some of the available information.  Ignoring information could lead to non-optimal decision policies, but often it is impossible to compute the exact policies (because the state space of the available information variables is too large).  Ignoring some of the information makes it possible to compute an approximate solution.