We present the architecture and design details of a logic database system that extends functionality in a number of ways. The system supports indefinite (non-Horn) facts in extensional database (EDB) and existential quantification in intensional database (IDB) rules. Semantic query optimization is integrated as part of the query processing module. The system also deals with efficient rule management for IDB and integrity constraints (IC). The proposed system supports the following database: The EDB consists of a set of positive ground formula, not necessarily Horn; The IDB includes rules that are Horn and may have existential quantifiers. The IC includes range-restricted Horn clauses with no existential quantification.