Databases have become an integral part of the modern society. In everyday life, we encounter several activities that involve use of databases such as withdraw of money from bank, getting railway reservation tickets, issuing a book from library, etc. When database of a large application is designed, the database designer has to deal with its large sized schema. He/she faces problems related to its representation, communication, comprehension, and documentation. This thesis addresses the problem of large sized database schema prepared using Entity Relationship (ER) model and proposes two solutions to deal with it. In the first solution, a schema compression methodology is proposed, and in other solution, a semantic modeling methodology for databases is suggested. The methodologies are useful for database designers facing problems in managing large sized database schema.