 Today's students there can be various approaches of developing web based database application, but there are certain basic building blocks which of course I will cover in this module and those basic building blocks are mapped across traditionally three type of architectures one tier architecture, two tier architecture, one tier is not something very useful in a production environment, two tier architecture and the three tier architecture, the web based database applications are basically developed based upon the three tier architecture. So first I'll go through the those basic four building blocks and then I'll be talking about those architectures. So this is the the module coverage, which I will be following in this module. So what are the components of a database application browser or presentation layer browser is the client, it could be Explorer, it could be Chrome, it could be Firefox. So what the browser does the browser creates the page for you based upon whatever text it gets whatever found it gets the commands. And it also runs embedded applications which it supports. Where is the use of the browser? So what the browser gets the browser gets from the business layer. Right. So these are the four building blocks which I mentioned. What is the business layer does it collects the data or information and it prepares it retrieves at formats. So the message over here is that this is not a static web page is a dynamic web page because it is retrieving it is formatting retrieving the data from all the way from the database server all the way from there and depending upon the commands which were given formats a page for you. Okay. And prepares the page for you. So these are the different tasks done by the business layer. Most of the time is spent by the programmers in the business layer. Why because how the business works, the business logic, the operation of the business is built into the business layer. Business layer doesn't mean it's a trade. It means for example, if it's a university environment, how GPS calculated, how the warnings are issued, what are the requirements for observing and monitoring the graduate studies of students and so on. That is something which goes in the business layer. Understand. So this is the most important layer because all the working is there. And then we have the database connection layer. The database connection layer basically connects your business layer with your database layer or the database server. Right. And what does the database layer is does it is storing the data. It is retrieving the data. It is updating the data is storing the data retrieving the data and updating the data. And where this all is done, it is done on the database, it is all done on the database. Okay, these things are happening over there. Okay, understand everybody. So this is the layered approach. Things are happening in the layers that allows maintenance and so on, which I have covered in prior modules also. So as I showed you in the earlier slide, we have the one tier application or the architecture and the two tier architecture and the three tier architecture. When tier architecture is that you want to practice a SQL, you install a database application on your machine is a laptop or a PC, you install a database on it, application on it, and you're running SQL commands on it, that is a one tier application or the architecture. It is not using production environment. Okay, this is not for production, not for production environment. Okay, then we have this two tier architecture. In the two tier architecture, what we have is that we have the client tier, and the client tier has the four modules which I showed you in the previous slide out of those four, three of them are in the client tier, include the business layer also. Understand. So now what will happen? You have this presentation layer also, and you have this business layer also. Okay, it will result into a fat client, fat client, fat client, it means that you need to have more of the processing power. It means you need to have more memory, which is against the concept of a web database applications because we would like to have a thin client, less processing power, less memory, so that there are more users, because more users can afford thin clients. But of course, this is the two tier architecture. This is like the traditional client server architecture, which I discussed in the previous slide. And next we have the three tier architecture. So we have this three tier architecture. And as you can see, things are properly bifurcated. Okay, so this database server is in the database tier. And usually, this is on a separate machine, this is on a separate machine and this is on a separate machine. PC 123 is not a kind of misnomer, but this is the PC, this is a server. This is a server. What is a server? Server is a high performance machine, high as compared to your PC. And of course, with this kind of an arrangement, you not only get better performance, you get better maintainability, better manageability, better deployment ability, and better security also, because you have divided your application into tiers. And you have these boundaries over here and you can have control over here. So these are the benefits of the three tier architecture, which is the basic architecture, the fundamental architecture for all web based database applications, scenarios, concepts, which we will be covering, which we have covered in this course. Thank you very much.