 Now in this module, I'll talk about the internet service provider, the database service provider, different types of the servers, and most important, most important is the people aspect with reference to technology. Because as I have experienced and if others have also experienced, you have to look at the people aspect. I'll talk more about. So any experienced developer would always advise the young ones that never get stuck or never get in a domain or set settled or concrete fixed with a certain technology with a certain service provider with a certain type of doing things. Why? Because things are changing. Things always change. The only constant is the change. And in the domain of computing and the web years is like history. The point I'm trying to make over here is that, for example, you are thinking about change moving to a certain platform. Now the provider of that platform will always tell you that this is excellent super and you will convert all what you have into the platform provided by that provider. Ask the question that how and how and what to do of converting from that platform, your data, your files into the format of some other provider. That is the key. It's like shuffling your table and chairs in your office until you are comfortable. So what we'll talk about very briefly is ISP internet service provider, DB database provider, different types of software, what are the three types or four types of database software and of course, CGI scripts and transitions. Transitions is the people issue. So internet service provider is the company or the organization that takes you to the internet. And DB hosting is the service provider where you have your application running. And at the back of your application is the database. Now you can have your internet service provider and the database service provider both together. That is fine. There's nothing bad about it. But as the traffic comes to your site, as your load increases, as your data increases, maybe you need to separate them. Maybe you need to have them web hosting separate from database hosting. Of course, there are advantages and there are benefits of having them together and having them differently. But the biggest advantage is taking care of the load. So you can have your database hosting on a separate server or you can look at the cloud option also, which we have discussed in the prior modules. It will be AS database as a service. And of course you can have your databases in a relational mode or in a non relational mode hosted on the web. And also consider when you are considering hosting your database, what management tools are provided by the database service provider, what features they have and do they allow to access only through those features and also access your database using standard query languages. You need to consider all those things if you have to grow. Now there are different database software. We have the basic database software. Then we have the middle tier. Then we have the higher end and then we have something which is called as the DC and support systems, which is not part of this course, but was part of the course CS 614. So we start with the basic desktop databases over here, basic desktop databases like access. Now over the period of time, what has happened is that these databases have become networked and multi user. That has happened so they have become networked and multi user. Then we have this object oriented databases where you can have object oriented paradigm implemented in the context of databases. We have over here database and we have others also where you can do the programming for this purpose. Okay. And then we have these enterprise databases. These are mostly relational. These are mostly relational like Oracle like SQL server. Right. So these are the relational databases and they have their own servers also. They have their own database servers with these applications. And then we have the data warehouse like data where the data comes from heterogeneous sources and the data sizes are large also. So these are the six different flavors. Let's move ahead. So what is the application server? Now the application server and what is a web server? What is the database server? Now in the context of the application server, you have your business logic over there where all the business logic is there. Okay. And you are generating your web pages over there. Okay. And you are getting all the formatic information. And then you have this database server. The database server is where which is to which you access your database. Now you may be accessing your database which can be relational like Oracle or DB2. Or you can be accessing a no SQL. No SQL means. These are the non relational databases. So you have all kinds of different servers. So what is a server? A server can be hardware or a server can be software. So sometimes these things can be a pair to be used interchangeably. But whenever they are used from the context, it is clear whether it's a software or a hardware. Okay. And finally, we connect all those things together to see that you make a request to your tier one. And that request goes to the tier two. Right. And we are assuming that your request over here consists of a database query. And it goes to the tier three, which is a database server. And you have your database over here, which is shown over here also. And then you have these results. You have these dynamic pages, which are sent over here and you can see what you wanted over here. Okay. So this is a picture which ties down all the things ties down all the three tiers. We'll talk more about these tiers also. And finally, the transition transitions. Now nothing is forever. Things change. Right. There was the time and maybe it's some part of the world that we have those tell net terminals, which are connected to a server and a lot of work may have gone or must have gone into developing such applications. And people are associated with those applications. Okay. And moving from old to new has its own challenges. There is resistance to change. But remember that the cost, the flexibility, the maintainability, the power of web based database applications is much, much better as compared to their old systems. But people are tied to those old systems. And they may not be very flexible in adopting the new systems. But there's no good in making excellent systems, which nobody is going to use. So my dear students, it is the people issue. It is not the technology. That's all I have to say in this module.