Entity Relationship Data Model

Database Concepts

• A database system has a self-describing nature, with a DBMS catalog storing the description of a particular database (e.g., data structures, types, and constraints) as meta-data.

Characteristics of the Database Approach

• The database approach allows for isolation between programs and data, called program-data independence, which enables changing data structures and storage organization without having to change the DBMS access programs.

Data Abstraction

• A data model is used to hide storage details and present users with a conceptual view of the database.
• Programs refer to the data model constructs rather than data storage details, supporting multiple views of the data.

Sharing of Data and Multi-User Transaction Processing

• The database approach allows for sharing of data among multiple users and multi-user transaction processing, enabling concurrent users to retrieve from and update the database.

Database Users

• System designers and implementors design and implement DBMS packages, interfaces, and test and debug them.
• Tool developers design and implement software systems for modeling and designing databases, performance monitoring, prototyping, test data generation, user interface creation, and simulation.
• Operators and maintenance personnel manage the actual running and maintenance of the database system hardware and software environment.

Advantages of Using the Database Approach

• Controlling redundancy in data storage and development and maintenance efforts.
• Sharing of data among multiple users.
• Restricting unauthorized access to data.
• Providing persistent storage for program objects.
• Providing storage structures (e.g., indexes) for efficient query processing.
• Providing optimization of queries for efficient processing.
• Providing backup and recovery services.
• Providing multiple interfaces to different classes of users.
• Representing complex relationships among data.
• Enforcing integrity constraints on the database.
• Drawing inferences and actions from the stored data using deductive and active rules and triggers.

Additional Implications of Using the Database Approach

• Flexibility to change data structures as new requirements are defined.
• Availability of current information, extremely important for on-line transaction systems.
• DBMS may provide protection or security measures to prevent unauthorized access.
• DBMS may provide "active" processing to take internal actions on data.
• DBMS may provide presentation and visualization of data.
• DBMS may provide maintenance of the database and associated programs over the lifetime of the database application.

Application Activities Against a Database

• Applications interact with a database by generating queries and transactions.
• Applications must not allow unauthorized users to access data.
• Applications must keep up with changing user requirements against the database.

Example of a Database

• Mini-world entities: STUDENTs, COURSEs, SECTIONs (of COURSEs), (academic) DEPARTMENTs, and INSTRUCTORs.
• Relationships between entities:
  • SECTIONs are of specific COURSEs.
  • STUDENTs take SECTIONs.
  • COURSEs have prerequisite COURSEs.
  • INSTRUCTORs teach SECTIONs.
  • COURSEs are offered by DEPARTMENTs.
  • STUDENTs major in DEPARTMENTs.

Learn about the relationships between entities in a conceptual data model, including sections, courses, students, instructors, and departments. Understand how these entities interact with each other.