Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • Free Essays • My Term Papers • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Computers Server Side Processing Server Side Processing A network is a group of two or more computer systems sharing services and interacting in some manner. In most cases, this interaction is accomplished through a shared communication link, with the shared components being data. Put simply, a network is a collection of machines that have been linked both physically and through software components to soothe communication and the sharing of information. The Internet is, literally, a network of networks. It is made of thousands of interconnected networks spanning the globe. The computers that form the Internet range from huge mainframes in research establishments to humble PCs in people's homes and offices. The Internet has become a very important learning tool. It is used for day-to-day activities, such as a place to look up research, a method of getting in touch with friends and family, and somewhere to go to find information about almost anything imaginable. The most popular uses of the Internet include entertainment and education. The objective of this paper is to constructively discuss and show the many components of the internet such as Server Side Processing, Client Side Display, Java Servlets, ASP, CGI, and more. The phrase server side processing (SSP) refers to what is commonly called SSI or server-parsed html, or a number of other things. These refer to when the server parses the HTML file, looking for strings that cause it to add content or remove from the HTML that is going to be delivered to the client. Typical uses for SSP are including the current date, the date the file was generated, the client’s login name, visitor counters, or selecting alternative text based on the HTTP headers of the request. This means that web applications on the other end of the wire from the web browser is a web server. The web server is the entry point to the Middleware Layer. The purpose of the Middleware Layer is to accept incoming requests and process them, using the resources provided by the web server, the machine that the web server runs on, or by the network of servers and resources that the web server is connected to. For example, one of the most basic functions of a Web server is distributing HTML files. In this case, a web browser requests a given HTML file from the web server. In response, the web server will find the given file on the local (or networked) file system and send it back to the browser. The web server has at its disposals a whole world of resources beyond file systems. Web servers are in close contact with all sorts of resources including data stores, applications, business objects, operating system resources, authentication services (server-based or directory services like LDAP/ADSI) and more. Although Server Side Processing has many advantages, it also has some disadvantages. For example, the useful things done with SSP are static, and can be generated when a document is generated. Parsing a source document once to generate the documents actually served will use much less CPU than parsing the document every time it is served. To select between documents, having the server select between static documents takes much less CPU than parsing the HTML as it passes through the server. Furthermore, SSP doesn't work with caches. If a document is cached, users start seeing the wrong version of the document. For the cases where the document is not cached, it must be re-fetched - even if unchanged - for every load. This increases the network load across the entire network. And because the average end-user bandwidth goes down instead of up, this is quite a disadvantage. In conclusion, SSP appears to serve no useful purpose which pre-processing documents cannot provide. Further, it causes both extra CPU usage on the server and extra bandwidth usage on the entire network while doing so. A client is a computer used to access network resources and a server is the networked computer that responds to client requests for network resources. The client side display (browser) environment provides the front end to an application. In this environment, for example, you display HTML pages in windows and maintain browser session histories of HTML pages displayed during a session. The objects in this environment must be able to manipulate pages, windows, and histories. On the other hand, in the server environment you work with the resources on the server. For example, you can connect to relational databases, share information across users of an application, or manipulate the server's file system. The objects in this environment must be able to manipulate relational databases and server file systems. In addition, an HTML page is not displayed on the server. It is retrieved from the server to be displayed on the client. The page retrieved can contain client-side JavaScript. If the requested page is part of a JavaScript application, the server may generate this page on the fly. Servers and clients have many dissimilar capabilities such as: · Usually (though not always) high-performance workstations with fast processors and large storage capacities. · Can become overloaded when accessed by thousands of clients. · Are often desktop systems with less processor power and storage capacity. · Are often single-user machines, so it can be advantageous to offload processing to the client. · Preprocessing data on the client can also reduce bandwidth requirements, if the client application can aggregate data. In conclusion, there are usually a variety of ways to partition an application between client and server. Some tasks can be performed only on the client or on the server; others can be performed on either. Use client processing (the SCRIPT tag) for these tasks: 1. Validating user input; that is, checking that values entered in forms are valid 2. Prompting a user for confirmation and displaying error or informational dialog boxes 3. Performing aggregate calculations (such as sums or averages) or other processing on data retrieved from the server 5. Performing other functions that do not require information from the server Use server processing (the SERVER tag) for these tasks: 1. Maintaining information through a series of client accesses 2. Maintaining data shared among several clients or applications 3. Accessing a database or files on the server 4. Calling external libraries on the server 5. Dynamically customizing Java applets; for example, visualizing data using a Java applet. Lets say a Web Site added convenient navigation to all of its pages. Some of those links sit within pull-down menus to save space on the left hand side of the screen. The menus are typical JavaScript menus, but they present two common problems: First, JavaScript does not work if the browser cannot support it. Second, JavaScript does not work if the client has the JavaScript option toggled off. Server-side help is needed for the pull-down menu to ensure that users can get to a chosen destination. When JavaScript is toggled off and a menu item is selected, the servlet sends the client to the requested page. Java Servlet technology handles this functionality. Servlets enable client/server communication, and because they're written in the Java programming language, they can use the power Java APIs (Application Programming Interface). As server-side applications written in the Java programming language, servlets can create interactive web pages, process forms, search web sites, manage sessions, cookies, and logins, and provide back up for other technologies such as JavaScript. A form is a powerful web site tool, enabling clients to take polls, enter personal information for online shopping, or subscribe to an e-newsletter. In other words, forms turn static web pages into dynamic pages. But a form cannot give instructions to a server. Without an application between the form and the server, the form is useless. Servlets process form information in three steps: What can be done with a servlet can also be done with a CGI (Common Gateway Interface) script, but servlets have a distinct, important advantage--once a servlet is invoked, it is NOT necessary to start a new server process with each request since the servlet stays in memory. CGI scripts, on the other hand, use heavyweight server processes for each request. Low traffic sites may not notice much difference between a script versus a servlet, but a site with heavy traffic loads would have a noticeable performance improvement by using servlets instead of CGI scripts. The Common Gateway Interface (CGI) is a standard for interfacing external applications with information servers, such as HTTP or Web servers. A plain HTML document that the Web daemon retrieves is static, which means it exists in a constant state: a text file that doesn't change. A CGI program, on the other hand, is executed in real-time, so that it can output dynamic information. For example, a Unix database wants to be connected to the World Wide Web, to allow people from all over the world to query it. A CGI program must be created that the Web daemon will execute to transmit information to the database engine, and receive the results back again and display them to the client. This is an example of a gateway, and this is where CGI got its origins. There is no limit as to what you can connect to the Web. The main thing to remember is that whatever the CGI program does, it should not take too long to process. Otherwise, the user will be staring at their browser waiting for something to happen. Since a CGI program is executable, it is basically the equivalent of letting the world run a program on your system, which isn't the safest thing to do. Therefore, there are some security precautions that need to be implemented when it comes to using CGI programs. CGI programs need to reside in a special directory so that Web servers know to execute the program rather than just display it to the browser. This directory is usually under direct control of the Webmaster, prohibiting the average user from creating CGI programs. There are other ways to allow access to CGI scripts, but the Webmaster must set these up. Perl (Practical Extraction and Report Language) is not a CGI-specific programming language. It is a powerful language with many applications far beyond the needs of CGI. Perl is one of the most common scripting languages used to write CGIs for Web sites. It is easy to use, and available for most platforms. Perl is an interpreted programming language with a number of features that make it very useful for manipulating textual data. As such, it is a good choice for a number of applications, including server gateways for HTTP servers. Perl's interesting features are: · No need to explicitly declare variables. Instead, the first character of a variable reference distinguishes between scalar, array or associative array. · No need to pre-declare the size of strings or of arrays. These start small and grow as large as necessary. · All variables have predictable default values until explicitly set. · A very rich set of pattern-matching operations that make it very easy to locate and process patterns of text. · A complete set of arithmetic capabilities. · A very complete set of built-in functions for a variety of tasks. · A rather bizarre syntax that is sort of like 'C', but different in a number of ways. · An orientation toward getting the job done quickly, rather than elegantly. Perl is interpreted, which means that no separate compilation step is explicitly necessary. Rather, one uses any text editor to prepare a text file containing the program source. The Perl processor then reads the whole file, converts it to an internal form and executes it immediately. PHP is a scripting language that is embedded in HTML and interpreted by the server. It can be used to manage dynamic content, work with databases, handle session tracking, and even build entire e-commerce sites. It works well with a number of popular databases, including MySQL, PostgreSQL, Oracle, Sybase, Informix, and Microsoft SQL Server. PHP codes begin with the tag *?php and ends with ?*. This tells the server that everything between *?php and ?* needs to be parsed for PHP instructions, and that if they're found, they need to be executed. Note that when your document is processed and served, the client as plain HTML will receive it. Someone browsing a site will not see any PHP instructions, unless an error is made and the server spits them out as-is instead of processing them first. PHP also allows the user to define their own functions. This makes PHP a language capable of providing a huge number of solutions via the Web.. Another different type of technology that augments the Web is ASP. ASP stands for Active Server Pages. It is a program that runs inside IIS (Internet Information Services). ASP is a Microsoft Technology and has the file extension ".asp". An ASP file is just the same as an HTML file and can contain text, HTML, XML, and scripts, which are executed on a server. An ASP file normally contains HTML tags, just as a standard HTML file. In addition, an ASP file can contain “server scripts, surrounded by the delimiters *% and %*. Server scripts are executed on the server, and can contain any expressions, statements, procedures, or operators that are valid for the scripting language you use”. Active Server Pages differs from HTML in many ways. One way is that when a browser requests an HTML file, the server returns the file, but when a browser requests an ASP file, IIS passes the request to the ASP engine. The ASP engine reads the ASP file, line by line, and executes the scripts in the file. Finally, the ASP file is returned to the browser as plain HTML. You can run ASP on your own PC without an external server. To do that, you must install Microsoft's Personal Web Server (PWS) or Internet Information Server (IIS) on your PC. ASP code cannot be viewed in a browser, only the output from ASP can be viewed which is plain HTML. This is because the scripts are executed on the server before the result is sent to the browser. In conclusion, ASP can do many things. It can dynamically edit, change or add any content of a Web page, respond to user queries or data submitted from HTML forms, and access any data or databases and return the results to a browser. ASP can also customize a Web page to make it more useful for individual users, provides security since ASP code cannot be viewed from the browser, and smart ASP programming can minimize network traffic. To put it bluntly, the advantages of using ASP instead of CGI and Perl, are those of simplicity and speed. 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