Truth Maintenance Systems
Derivation Record
- Records a derivation whose conclusion is added to the KB
- Includes
- The conclusion
- The sentences from which the conclusion was derived
E.g., S3 was derived from S1 and S2
Support for sentence S in a KB
- Set of derivation records in which S is the conclusion
- A record of whether S was “told”
When a sentence S is “untold” from a kb:
- Consider each recorded derivation D supported by S
- Untell the conclusion of D if it is:
- Not supported by any other recorded derivation
- Was not told