PaLM is a:

• constraint solver
  PaLM is a fully featured constraint programming system handling arithmetical constraints, CSP-like constraints, symbolic constraints (element, allDifferent, ...), boolean combinations of constraints, ...
  The explanation-based features of PaLM can be completely set appart to provide a classical constraint programming: note that explanations will still be used for search !

• explanation-capable constraint solver
  PaLM does not only solve constraint problem but is also able to provide explanations to the user on what has been done:
  • Why my problem does not have any solution ?
  • Why variable x cannot take value a in a solution ?
  • Why is variable x currently assigned to a ?
  
  PaLM provides tools to access this information in a user-friendly way.

• dynamic constraint solver
  PaLM allows to dynamically add and remove constraints
  • before solving: to interactively modify the problem to be solve
  • during solving: to be able to add or/and remove constraints in response to outside modifications
  • after solving: to be able to reuse a solution and to continue the search.
  
  PaLM is a completely interactive constraint solver.

• over-constrained problem solver
  PaLM can also solve over-constrained problems by combining the two preceding features (explanation capabilities to determine set of constraints responsible for lack of solution and dynamic capabilities for dynamically removing responsible constraints).

• e-constraints programming system
  Explanations have many more usages (see the applications page for an overview) and PaLM provides many tools to take advantage of explanations.

• PaLM is finally a claire ¹   module to be used as a choco ²   extension. You can download it here.

The manual and online tutorials illustrate those facets of PaLM.