 So, we talk about how databases work on the web. This module will cover about 3 chapters from the textbook and the purpose of this module is to give you an idea about what material will be covered in those 3 chapters. So, collectively those 3 chapters constitute about 30 pages. Of course, that is not possible to cover those 30 pages in this module. So, this module will give you an idea what is there on those 30 pages in those 3 chapters. So, this is about the story so far about what is the story? The story is that over the period of time the processing power has increased for the computers. The cost of the computers has gone down. The cost of telecommunication has gone down. The bandwidth has gone up. There is a lot of requirement of applications which cost a lot of money for customized development. And there is a requirement of having access. The interface issues are there. So, all of these things have been fueling what the web-based database applications. And the trend change has been from the old dump terminals connected to the main frames. Then came the PC revolution. Then came the operating systems. And then of course, the worldwide web. So, that was the story so far. Now, dump terminals and main frame, the issue with these aspects was that the application had to take care of many things. And the application was running on the main frame. The terminals, they are dumb because they didn't had or had very little processing power. So, that terminal was the client's interface with the web server, with the application server or the main server. So, to say, that was several decades ago. Then came the operating system. And came the structured programming. The benefit of operating system from the application point of view was that the programmers didn't had to write the commands in the applications which were running on the server. Those operations that power their commands were within present in the operating system. And then with the availability of the structured programming, there was the additional benefit of the reusability of the code. So, these things were fueling what we are discussing today. And then came the personal computers. With the personal computers, the cost of the machine went down. The operating system was available within the personal computer. And we had that client server architecture. So, processing was done at the client end, which was the PC. And the main processing was of course done at the main server, which was the server over there. And then came the internet. Now, the thing is that the internet was around in 1960s, since 1960s. But it became popular widespread when it went out of the research organizations. When it went out of the ARPA, which was the department which developed the internet, and it became very widespread. And it was using TCP IP. Now, these protocols were not meant for e-commerce. These protocols were inherently not secure, not strong enough to ensure authentication, to ensure validation, to ensure privacy. And of course, the data was available on the net when it was being exchanged. It means that the prospects of integrity or the issues with the person with very little skill was there for maligned intentions. So, that is why things have to be catered for. Now, this is the second chapter, internet service providers and database service providers. Now, try to understand that if I have my mobile phone and I am accessing the net, we are not talking about it. We are talking about a database application which is connected to the internet, right? The connected to the internet, my mobile phone is the client. I am using it to browse the web, to make use of the web application. The big difference. So, when I have a web application, that application is on my PC, is on my server. So, do I have to connect this to the internet? For that, I need an ISP, internet service provider, or I need a database service provider. The database service provider where my application is running. There can be many modes. I will briefly go through all of them. Of course, the details are in the main chapters. And then is the database software. So, the database software falls into three categories. One is the database software that was developed for desktop applications. For example, access, for example, X base. Now, over the period of time, their multitasking versions and their online versions, or the network versions became available. Then there is the second category that was object-oriented databases. For example, we have that DBase next version. And we have other, Visual Fox Pro also. Object-oriented developed in Java. And then we have the high-end databases. For example, for the enterprises like Oracle, like DB2, like SQL Server. So, these are the databases. And then we have what is called as the CGI scripts and Perl. Common gateway interface. These scripts can be written in Perl. They are platform-independent. And using these scripts, one can connect your MyCury to the web. Over the web, it goes to the web server. And from there, it draws the results for which I have submitted the query. So, I can write CGI script in C. I can write in C++ also. And of course, we can use Perl for that purpose. So, CGI script, another purpose served by CGI script is that it is the glue which ties together all the components of a web-based application, which is a database application. And then is the transitions. As I have said before, in the older client server models, of course, I'll talk about the second tier and third tier models also. The people are used to using those models. They are used to using those models. They may be very inefficient as per the current trends and as per the current requirements. But people are comfortable with it. Now, when you come up with an idea of replacing those models, replacing those systems, you are going to face a lot of opposition. At this point, some very interesting quotation comes to my mind, which is that change comes with pain. And if you are in not enough pain, then you are not ready for change. I go to the next chapter now. This module covers about three chapters. Choosing your internet service provider. Now, the internet service provider, do I need a service provider for mail, to send mail, to receive mail, to perform file transfer FTP, to do what? Or I need for the database services. So how many do I need? How do I get started? Which is the starting point? Remember that using my phone, I browse the web. I run the application, which is on the server. I am talking about connecting my application, which is running on my web server, on my data server. And I need to connect it to the internet. For that, I need a web server. And I need an internet connectivity. So talking about the domain names. Now, domain names are important. Domain names are important, the reason being over here, that this domain name carries my identity, which I discussed earlier, module also. Now, using this domain name, if this domain name lies within the name of the ISP and I move my application, then I have to change it with the ISP. That is very inconvenient. So I need a domain name, which is gestured with me and changes with me and moves with me. Now sending mail and receiving email over here. Remember that on the internet, there is no check that I may be sending an email from an address, which is not my address. So for this, I need to cover it. And then of course, these are different types of connections. Dial-up connection is I connect my web server, my database server with the internet service provider over a dial-up line and the IP address is dynamic. Then of course, the next is the dial-up connection with static IP. I get a fixed IP. With static IP, my IP is changing and people will have difficulty locating me over the internet. With the static IP, it doesn't changes. Of course, there are advantages, there are disadvantages and there are other issues and considerations also. Then I have a non-switched connection. This non-switched connection is based upon a frame relay, is based upon ISDN, is based upon Lee's line and then is the co-location. Co-location and database hosting, all of these things and of course e-commerce and other services are also provided by the ISP. Details when we come to those modules.