Abstract: An RDF reason maintenance system avoids imposing a scalability restriction on the number of explicit statements stored in RDF databases. The system can identify those inferred statements that suitably should be removed whenever an explicit statement is deleted (retracted). The system dynamically computes the truth using a combination of the forward-chaining hardware and the backward-chaining hardware. The system is time-efficient, computes faster than a full re-computation, and need not use any long-lived truth maintenance information (space-efficient).