The paper presents an unified Description Logic (DL) model for databases. Describing database models using DLs is a fundamental problem in many areas because it turns databases to logical systems with enriched semantics and enhanced reasoning mechanism. A typical relational database model comprises three components: relational data model, relational operations, and queries. Therefore, a DL model for databases should also unify these three components together. However, most available DL models for databases only describe one or two components of database models. After pointing out the two key factors resulting in the absence of such a model, the paper develops an extended dynamic description logic language DALCP based on PDLC with enriched form of action modal operators. Based on PALCP , an unified DL models for databases is presented. It represents relational data by ALC, represents relational operations by atomic modal operators representation; and represents queries by complex modal...