Chapter 7, Problem 2M

What distinguishesa weak entity from a strong entity that has a required relationshipto another entity?

When is it important to use an associative entity to express a many-to-many relationship?

Entity-Relationship Diagram (ERD) is one of the data modeling tools that provides a software engineer with the ability to represent data objects, their characteristics, and their relationships. Use an ERD to describe the following scenario. A teacher is identified by an ID number (TID), last name (LName), and first name (FName). A project is identified by a project ID (PID) and title (T). A student is identified by an ID number (SID), last name (LName), and first name (FName). A teacher can supervise zero, one, or many students and a student is supervised by one teacher. A teacher must propose one or many projects and every project is proposed by one teacher. A student must work on one project and every project is worked by only one student.

Explain the distinction between entity type and entity instance.

ENHANCE ENTITY RELATIOSHIP DIAGRAM The entity type PERSON has the following attributes: SSN, name, address (City/State/Zip), date of birth, age, and contact number. The entity also has the three subtypes: CAMPER, BIKER, AND RUNNER. Draw a separate diagram segment for each of the following situations:  1. At a given time, a person must be exactly one of three subtypes. 2. A person may or may not be one of these subtypes. However, a person who is one of these subtypes cannot at the same time be one of the other subtypes. 3. A person may or may not be the one of these subtypes. On the other hand,  a person may be any two (or even three) of these subtypes at the same time.  4. At a given time, a person must be at least one of these subtypes.

Draw an Entity Relationship Diagram for ther following information.

Define an entity-relationship model and describe its purpose

List the Entity-Relationship (ER) model's various characteristics.

Describe the Entity-Relationship model and its function.