Internet
Simply put, the Internet is a complex network comprising billions of interconnected computers. The computers connected to the Internet, called hosts, communicate with one another using a set of standard procedures, called a protocol suite. In particular, the so-called Internet Protocol, or IP, is responsible for providing addresses for hosts and for routing packets of data from a source host to a destination host across the network.
The Internet supports any communications protocol built on top of the Internet Protocol. The most common one is the so-called Transmission Control Protocol, or TCP, which provides reliable and error-free transmission of data between hosts. Together, they are known as the standard Internet protocol suite, referred to as TCP/IP.
World Wide Web
The World Wide Web, commonly known as the Web, and abbreviated as WWW or W3) is a collection of specially marked documents, called hypertext documents, that are accessed through the Internet.
Hypertext documents may include text as well as several kinds of multimedia content that are connected by means of hyperlinks.
A Web Site is an example of application built on top of the WWW. Most typically, a user accesses the Web with a browser, such as Internet Explorer, that requests documents, images, and other kinds of resources. These are then returned by a host called "Web server" and displayed in the browser window on your screen.
Although sometimes they are incorrectly used as synonyms, the Web should not be confused with the Internet, which is the infrastructure enabling the Web.
Client-Server Architecture
The Web may be regarded as a distributed client-server system. This means that some computers (the clients) request resources or services, while other computers (the servers) respond to such requests. The Web adopts a protocol named HyperText Transfer Protocol, or HTTP, that specifies how a client and a Web Server may interact.
Among the main elements identified by the HTTP protocol are:
- The browser, which connects to a server to request some resources asked by a user, and displays the results on the user interface.
- The Web Server, which locates or computes the requested resource and sends it back to the client through the network.
Each resource exchanged by clients and servers is uniquely identified by a Uniform Resource Locator, or URL. A URL is a string, typically visible in the address bar of a browser, that contains a host name and, optionally, a port, a path, and a query.
Three-Tier Architecture
Web applications are normally structured in three main tiers:
- The Presentation Tier refers to the way information is eventually shown to the end user in a comprehensible way. The browser is the component that usually takes care of that presentation by communicating with a Web server. In most cases, the Web Server returns pages formatted according to the HyperText Markup Language, or HTML.
- The Data Tier is where the data relevant for an application resides, hosted by one or more database servers.
- The Application Tier controls how an application functions by performing calculations and making decisions compatible with the application's business logic. The software that takes care of this aspect usually runs in a so-called Application Server, a machine that connects to the Web Server on one side, and to the database server on the other. The Application Tier is sometimes also called "Logic Tier" or "Middle Tier".
WebRatio Platform and the Web
With WebRatio Platform, all the aspects regarding Web applications are taken care of for you. WebRatio Platform allows you to easily design the data model of your application and to maintain a database that hosts your data. You can use either your own database or take advantage of the built-in database capabilities shipped with WebRatio Platform, which are based on the Derby database.
WebRatio Platform automatically deploys your Web application to the Application Tier. Again, you can use either the application server of your choice or the built-in solution available in WebRatio Platform, which is based on Tomcat. Finally, WebRatio Platform allows you to seamlessly connect to your Web application through the browser of your choice, or by using a built-in browser, integrated with the WebRatio Platform IDE.
External References
The development of Web applications involves a wide spectrum of technologies, languages, and frameworks. In this lesson, we have only scratched the surface. If you want to know more, you can consult several external sources that are freely available on the Web. The W3C consortium offers several short tutorials covering the topics discussed in this lesson in greater detail. Follow the links shown here to deepen your knowledge.
Acronyms
In this lesson, we have been using many acronyms, some of which may be difficult to memorize. Let's repeat them again.
- WWW: World Wide Web.
- HTTP: HyperText Transfer Protocol.
- TCP/IP: Transmission Control Protocol / Internet Protocol.
- URL: Uniform Resource Locator.
- HTML: HyperText Markup Language.