a powerful method for designing and querying database models at the conceptual level, where the application is described in non-technical terms. 1. Communicating models with your team 2. Communicating and validating models with your client 3. Great brainstorming tool In practice, ORM data models often capture more business rules, and are easier to validate and evolve than data models in other approaches.
Course named Math Entity Types: Student, Course Value Types: Ahmed, Math We have 3 Facts (predicates) with 2 roles each: - Student is named Ahmed - Course is named Math - Student is enrolled in Course
to follow these steps starting from the requirements provided by the domain expert: 1. Transform information examples into facts 2. Draw the Entity & value types 3. Add Fact types and assign roles 4. Add constraints
Type Student name, course name, song title, band name Fact with 2 roles (Predicate with 2 arities) Student is enrolled in course Uniqueness Constraint (has one) the first role is unique ti the second role. Each student has at most 1 name but there may be 2 students who have the same name 1:1 both roles are unique to each other Every student has at most one name and there are no 2 students with the same name. m:n Many to many Every student may be enrolled in many courses and each course may have many students. ORM Symbol Glossary Value Entity