Entity Relation Diagram is used to illustrate a unified view of a system data [1]. This entity relation diagram shows the main entities in LessonPlan application and how these entities relate to each others. By ensuring the correct entities data types and relation, we enforce the integrity of the database. The relationship between two tables is ensured by referencing its primary key like userid in Module_Feedback table which reference the user id who provided that feedback. If a user id does not exists in user table, it can not be stored in any other table which reference it. This is to enforce the referential integrity in database. To enforce the entity integrity, a primary key in each table has been identified. These primary key might be single attribute like userid in users table or composite primary key (consists of multiple attributes together) like mode_program table.

In ERD, U stands for unique in that table and N stands for nullable (can be null). To ensure that an email address is not used by two or more users, the attribute constraint is set to be unique. Same for school name, module name and program name as we can not have the same name which represent two schools, modules or program. The grade in user table is set nullable so the user will have the ability to choose between giving it or not.

These tables represents only LessonPlan database without the integration with university database in which the system can query from using remote procedure calls.

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[1] Chen, P. P. S. (1976).The entity-relationship model toward a unified view of data. ACM Transactions on DatabaseSystems (TODS), l(1), 9-39.