This is the sixth in a series of articles introducing the Visio-based database modeling component of Microsoft Visual Studio .NET Enterprise Architect. Part 1 showed how to create a basic ORM source model, map it to a logical database model, and generate a DDL script for the physical database schema. Part 2 discussed how to use the verbalizer, make an object type independent, objectify an association, and add some other ORM constraints to an ORM model. Part 3 showed how to add setcomparison constraints (subset, equality and exclusion) and how exclusive-or constraints combine exclusion and disjunctive mandatory constraints. Part 4 discussed the basics of modeling and mapping subtypes. Part 5 discussed mapping subtypes to separate tables, and occurrence frequency constraints. Part 6 discusses ring constraints.