 Hello and welcome to video lecture on Entity Relationship Model. At the end of this lecture, students will be able to identify Entity and Attributes in a given problem statement. Entity Relationship Model was proposed by Peter Chan in the year 1971 to create a uniform convention which can be used for relational database and network. He aimed to use this model as a conceptual modeling approach. The Entity Relationship Model is a high-level conceptual data model diagram. Entity Relationship Model is based on the notion of real world entities and the relationship between them. Entity Relationship Model helps you to analyze data requirements systematically to produce a well-designed database so it is considered a best practice to complete ER modeling before implementing your database. It is very useful in mapping the meaning and interactions. The ER model employs three basic concepts, first entity sets, relationship sets and attributes. An entity is a thing or object in the real world that is distinguishable from all other objects. Example, person, it may be a student, employee, patient or a doctor, place it may be a store or building, object it may be a machine or a car. Entity can be concrete like person or a book or it can be abstract like course or course offering. Entity is represented by its properties and values called attributes. An entity set is a set of entities of the same type that share the same properties or attributes. The set of people who are instructors at a given university can be defined as the entity set instructor. Entity set do not need to be destroyed. For example, it is possible to define the entity set of all people in a university. A person entity may be an instructor entity, a student entity or both or neither. An entity is represented by a set of attributes. Possible attributes of the instructor entity set are ID, name, department name and salary. Each entity has a value for each of its attributes. For instance, a particular instructor entity may have the value 12121 for ID, the value Biradhar for name, the value computer science for department name and the value 60000 for salary. A relationship is an association among several entities. For example, we can define a relationship advisor that associates instructor and a student. This relationship specifies that instructor is an advisor for the student. A relationship set is a set of relationships of the same type. Consider two entity sets instructor and student as shown in figure. We define the relationship set advisor to denote the association between instructor and student. The association between entity sets is referred to as participation. A relationship instance in an entity relationship schema represents an association between the names entities in the real world enterprise that is being modeled. As an example, the individual instructor cards who has instructor ID 4565 and the student entity Shankar whose ID is 12345 participate in a relationship instance of advisor. This relationship instance represents that in the university instructor cards is advising student Shankar. The function that an entity plays in a relationship is called that entity's role. Since entity sets participating in a relationship set are generally distinct, roles are implicit and are not usually specifies. When the entity sets of a relationship set are not distinct that is the same entity set participates in a relationship set more than once in different roles. This type of relationship set sometimes called a recursive relationship set. Explicit role names are necessary to specify how an entity participates in a relationship instance. For example, consider the entity set course that records information about all the courses offered in the university. To depict the situation where one course is a prerequisite for another course, we have a relationship set prerequisite that is modeled by an order pair of course entities. A relationship may also have attributes called descriptive attributes. Consider a relationship set advisor with entity sets instructor and student. We would associate the attribute date with that relationship to specify the date when an instructor become an advisor of student. A relationship instance in a given relationship set must be uniquely identifiable from its participating entities without using the descriptive attributes. For example, suppose we want to model all the dates when an instructor become an advisor of a particular student. The single valued attribute date can store a single date only. We cannot represent multiple dates by multiple relationship instances between the same instructor and a student. Since the relationship instances would not be uniquely identifiable using only the participating entities. It is possible to have more than one relationship set involving the same entity sets in our example. The instructor and student entity sets participate in a relationship set advisor. Additionally, suppose each student must have another instructor who serves as a department advisor. Then the instructor and student entity sets may participate in another relationship set department advisor. The relationship set advisor and department advisor provide example of a binary relationship set. Most of the relationship sets in a database system are binary. Occasionally, however, relationship sets involve more than two entity sets called ternary relationships. As an example, suppose that we have an entity set project that represents all the research projects carried out in the university. Consider the entity set, instructor, student, and project. Each project can have multiple associated students and multiple associated instructors. Furthermore, each student working on a project must have an associated instructor who guides the student on the project. We focus on the information about which instructor is guiding which student on a particular project. To represent this information, we relate the three entity sets through the relationship set project guide, which indicates that a particular student is guided by a particular instructor on a particular project. Note that a student could have different instructors as guides for different projects, which cannot be captured by a binary relationship between students and instructor. The number of entity sets that participate in a relationship set is the degree of the relationship set. A binary relationship set is the degree of two. A ternary relationship set is of degree three. Properties of the entities are called attributes. For each attribute, there is a set of permitted values called the domain or value set of that attribute. Formally, an attribute of an entity set is a function that maps from the entity set into a domain. Since an entity set may have several attributes, each entity can be prescribed by a set of pairs, one pair for each attribute of the entity set. An attribute as used in the entity relationship model can be characterized by the following attribute types, simple, composite, multivalued, and derived. Simple attributes, they cannot be divided any further. Composite attributes are possible to break down. Multivalued attributes can have more than one value. Derived attributes does not include in physical database. In our example here, a composite attribute name with component attribute's first name, middle, initial, and last name replaces the simple attribute name of instructor. As another example, suppose we were to add an address to the instructor entity set, the address can be defined as the composite attribute address with the attributes street, city, state, and zip code. The attribute street is itself a composite attribute whose component attributes are street number, street name, and apartment number. Figure also illustrates a multivalued attribute phone number denoted by curly braces and a derived attribute age depicted by age. Now, pause the video for some time, answer the following question. UPS Pride prides itself on having up-to-date information on the processing and current location of each shift item. To do this, UPS relies on a company-wide information system. Shift items are the heart of the UPS product tracking information system. Shift items can be characterized by the item number, weight, dimension, incidence amount, destination, and final delivery date. Shift items are received into the UPS system at a single retail center. Retail centers are characterized by their type, unique ID, and address. Shift items make their way to their destination via one or more standard UPS transportation events. These transportation events are characterized by a unique schedule number, a type, and a delivery route. Find the entities for the following problem statement. Answer is entity set. Shift item is an entity, and item number, weight, dimension, incidence amount, destination, and delivery date are the attributes. Similarly, retail center is an entity, and unique ID type are attributes. Transportation event is an entity, and type, delivery route, schedule number are attributes. Thank you.