``Top-Down'' Deletion Algorithm.

• It consists of two phases:
  1. Remove all the analysis information that depends on the deleted clauses.
  2. Restart analysis (using non-incremental algorithm).
• When we restart analysis, information that does not depend on the deleted clauses is already present.
• ``Top-down'' deletion of clauses produces the same analysis results as non-incremental analysis.
• Phase 2 of the algorithm cannot be worse than re-analyzing from scratch.
• ``Top-down'' deletion algorithm is pessimistic. Everything is deleted unless it is sure to be useful.
• In practice, it cannot be much better than re-analyzing from scratch.
• Deleting a single clause will remove half of the analysis information during first phase of the algorithm.