MatBase is a Knowledge Base Management System joint ly developed by DATASIS ProSoft srl and Ovidius Uni versity, based on the Elementary Mathematical Data Mo del (EMDM) and Datalog. Its Datalog subsystem uses a syntax-directed translation to relational algebra (RA) algorithm and a least fixpoint semantics evaluation en gine. The paper presents the conceptual design of both MatBase Datalog and RA meta-catalog in three forma lisms: Entity-Relationships Diagrams (E-RD), EMDM, and Relational Data Model (RDM) schemes.