 Students, in this module, I will briefly cover the relational model. We have been talking about the relational model for a while and we will also mention it in the subsequent slides also. It is kind of a review and kind of a refresher in the context of web-enabled databases. So when we talk of the relational models, okay, this or when we talk of the database behind our mind is the relational model. The relational model has been around for maybe more than three decades as of today and a lot of development has been taking place at the commercial level at the marketing point of view and from the mathematics and computer science point of view also. So let's look at the module coverage. So two simple points need to be considered, which I will talk about. And then there is about the objects and about the operators and about normalization and integrity. So these are some of the fundamental things of the fundamental aspects which are related to the relational model. So let's first talk about the two simple points. Okay, now those two points is that all the data is stored in a table. I am talking of the relational model. A table is a two-dimensional entity. Okay, and when the operations take place on a table, which I will briefly be talking about, the result is also a table. And of course that result could be a single record or it could be a cell only. It depends upon the nature of the table and the type of the query. So there are three parts of the relational model. First is the object. Object is what ever collectively constitutes a database, okay? What the relations, the tuples, the attribution, so on. I will be discussing them in the next slide. And then is the integrity. The integrity is the rules which are behind the relational model. And in this module, we will not be talking about those rules. And in the subsequent, you just ensure that those rules are followed. We will not go into the basics of those rules. And then the operators. The operators are the commands which are acted upon the tables. And of course they produce the results. And what the result is, that is again a table. As these two common things about a relational model. So what are the objects? The objects are the relations. What are the objects consist of all of those things, which you can see on your screen. All those things. So a relation is a table. That is an object. Attributes are the rows. Every record is a tuple, okay? That is in the relational terminology. Then the columns are the attributes, the values. For example, the name, the date of birth, okay? The address, these are all the attributes or the columns of the database. And a group or a single group of all those columns is an attribute. Then is the primary key. Primary key is that unique value based upon which you can retrieve the data from the relational model. For example, the ID card number CNIC of a person or the social security number of a person is that primary key, right? And of course the passport number is can be a primary key also. Then is the domain. The domain is the set of legal values which can be there in an attribute. For example, the attribute about the age, okay? For that domain value, green color is not a valid thing for that domain. It is just out of place. And then is the cardinality. Cardinality is the same terminology from the set theory also is the number of records or the number of tuples in the relations which is the tables and the degree. The degree is the number of attributes in that table or the database. So this is the, these are the objects. Now integrity and the operators, there are many types of keys. There is the primary key, there is the foreign key. Then there are other keys, integrity relationships. Integrity relationships means that if I'm inserting something in the database, that is with reference to something which already exists. I will explain this. And then are the unique keys, primary key is the unique key. There are two types of operators, the algebraic operators and the calculus operators. And for you, it is sufficient to work with the operators which we'll be using, which are very simple ones. And remember that of course there are many, many commands of SQL, SQL, which is the language used to retrieve data from the relational tables. But not all of those commands are being used. Now depending upon the command used, you can have or we can have a table which is larger than what we started with. And of course it can be smaller than what we started as you can see on the screen. And there is a normalization. The purpose of, as a matter of fact, you basic database design or the people who are making those simple databases, they might actually be doing normalization without knowing that they are doing normalization. So what is the purpose of normalization? The normalization purpose is to make the database efficient, okay? And it should be optimized to handle the processes. Because remember that we are making a system, okay? Now I'm looking at the application, not to share the data or not to for internal use. So we are making an application like the processing for the telephone calls made on a phone. So we want to make a system which is very fast. That is why we need normalization. There are five types of normalization, then there are other types also. But in this course, I will be not going into lots of details about all of those types because those types and the details are part of a course on database. That's all I have for this module for you.