If GORM (Grails Object Relational Mapping) is not flexible enough for your liking you can alternatively map your domain classes using Hibernate, either via XML mapping files or JPA annotations. You will be able to map Grails domain classes onto a wider range of legacy systems and be more flexible in the creation of your database schema. Best of all, you will still be able to call all of the dynamic persistent and query methods provided by GORM!