Object Role Modeling

Object Role Modeling Prepared by Ahmed Magdy Ezzeldin

Outline
What & Why ORM?
ORM Building Blocks
Example
ORM Process
ORM Symbol Glossary
Summary

What & Why ORM?
Object Role Modeling (ORM) is 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.

ORM Building Blocks
Object Types - Entity Types (map directly to an ER Entity ) - Value Types (map directly to ER attributes )
Facts - Predicates: {0} is enrolled in {1} - Roles: {0} and {1}
Constraints - Like uniqueness constraint

Example
The Student named Ahmed is enrolled in the 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

ORM Process To model any application using ORM we need 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

ORM Symbol Glossary Value Entity Description Symbol Example Entity Type Student, course, song, band Value 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.

Summary
ORM can be changed to ER .
ORM can easily be changed to UML .
ORM is rich as it captures more business details by capturing facts and constraints .

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Object Role Modeling

by Ahmed Magdy

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Object Role Modeling Presentation Transcript