Sunday, June 14, 2009

Creating Web Applications A Small Overview

System Input and Output

Since the user interface function takes place through a Web browser running on the PC client, you can use development tools that program the browser to perform output formatting, data entry, and data validation tasks, among others. For these purposes you need knowledge of markup languages such as XHTML and CSS (Cascading Style Sheets) to structure and present system input and output. Of increasing importance are markup language extensions such as DHTML (Dynamic HTML) for user interactions with the Web page and XML (eXtensible Markup Language) for representing data structures that are delivered by the server for processing on the browser. Also, the primary programming language for the browser is JavaScript, which is used to manipulate markup languages and data structures to perform browser processing tasks.

System Processing

On the Web server side you need to be able to write applications to perform the main processing activities of the system. Server languages such as Visual Basic and C# (C sharp) are used to code these routines. One the one hand, these languages function as full-features programming languages to code the arithmetic and logical details of processing; on the other hand, they call upon built-in server processing components to perform the main or ancillary work of the system. The Microsoft .NET technologies, implemented as ASP (Active Server Pages).NET, is one such collection of processing components. Through this set of software objects the Web programmer can perform virtually any processing task without having to code elaborate sets of detailed instructions. Of course, the energetic programmer can code Web applications in conventional languages such as C++, Java, and the like, or can code specialized software components callable through Visual Basic or C# for application of their processing functions to the task at hand.

It is more accurate to think of server languages such as Visual Basic and C# as scripting languages rather than programming languages. Their use is in tying together prebuilt components from, say, the .NET framework, moreso than in writing intricate processing details. This is becoming the nature of Web applications development, producing a logical roadmap of processing tasks which are implemented as preprogrammed, black-box components adaptable to specific processing needs. A Web script, rather than being a computer program, is a processing control structures to call upon available software components to perform the work of the system.

Database Management

On the database server side, languages such as SQL (Structured Query Language) perform the data storage, maintenance, and access functions to keep information up to date and accurate for Web presentation. In addition, database programming languages are used to code command procedures, processing functions stored within databases to extract from, update, and report on their contents. Server languages call upon these SQL commands and stored procedures to perform their associated processing, saving the developer from having to code the low-level access details directly. ADO (Active-X Data Objects).NET components provide the interface between scripting languages and these data access routines in order hide the complexity of data access. Of increasing importance in data storage and electronic data interchange are XML data structures. Being able to convert between standard file and database formats to XML formats is becoming a crucial Web development skill.

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