E-commerce Fundamental Technology

2.1 E-commerce Fundamental Technology

2.1.1 Web Technology

The structure of web technology is shown in Fig. 2.1. In this kind of architecture, web client means the terminal with a browser. Web server is the mainframe which stores multimedia data resources and provides www services. The middleware can invoke the database and other applications in the web server. Common middleware include CGI, JDBC and WebAPI.

Figure 2.1 Web technical structures The fundamental principle of web communication is as follows. The browser

sends http request to the www server. After receiving the request, www server will make response processing, and return the processing result to the browser in the form of html file. Then the browser will interpret and display it to the user. The interaction between www server and database server has to be connected by the middleware.

The web browser is an application, which seems like a word processing application (such as Word Perfect or Microsoft Word) at the client terminal. The webpage displayed on the computer screen is the interpretation of the html document. Instead of typing various commands with the keyboard, the browser with GUI has made it possible for the users to execute their operations by selecting the icons with the mouse, which is a great convenience to the users.

The web browser gets access to a designated document or service by sending request to the web servers based on http protocols. Correspondingly, the web server returns the responding document of the request. Then the browser interprets all the tagged codes and displays them in correct format. Browsers usually have the functions such as URL locating, hyperlink, offline browsing, searching and printing.

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2.1.2 HTML

HTML (Hyper Text Markup Language) is a simple markup language that is used to make hypertext documents. HTML documents are independent of operating system platforms (such as UNIX and Windows). Since 1990, HTML has been used to represent information on the Internet, including the definition of the format and style in pages and the relationships among several documents.

HTML documents (the source code of the page) is a marked up ASCII text, the file name is usually followed with .html or .htm. There are three ways to generate html file:

(1) Directly manual coding (using ASCII text editor or other HTML editors). (2) Transferring the exist documents in other format to html documents with

some format transformation tools. (3) Dynamically generated by the web server (or http server). Html marks the structure of the documents and the hyperlinks by using various

tags. Although it describes the structure of the document, it cannot define but suggest the way in which the document displays and arranges the information. The final result displayed in front of the user is determined by the display style and the explain ability to the tags of the web browser. That is why the same document will be displayed differently in different browsers. Now the version of html is 2.0, which evolves from a subset of the Standard Generalized Markup Language (SGML).

2.1.3 XML

XML is the extensible markup language, which is usually misunderstood as the simple extension of the HTML.

XML combines the advantages of SGML and HTML while eliminating their disadvantages. XML is still considered as a kind of SGML, which can realize most of the functions of SGML. In summer 1996, John Bosak of the SUN Microsystem began to develop W3C SGML (now called XML group). Their goal is to develop

a new SGML which has the advantage of SGML with the simplicity of html.

There are many projects of web mark language in special areas, for example, the chemical markup language (CML) developed by Peter Murray Rust. In mathematics, companies including IBM are engaged in developing MathML. In Apr. 1997 the first version of XL1 was released. When the XL1 was completed, its function would be more complicated and stronger than that of the current html and browser. In Feb. 1998, W3C released the formal version of XML1.0. With the rapid development of network applications, the development of XML is also popular in recent years. New terms such as DOM (Document Object Model) and XSLT (XSL Transformation) appear, and the application of XML is also developing very fast. Companies such as Microsoft, IBM, Breeze and Stilo turned out their own solution or development platforms. Thanks to the promotion made by

Introduction to E-commerce

Microsoft, Breeze, HP, etc., now there are two well-known XML research groups, biztalk.com and oasis.org. And they proposed the standards to W3C together. The former is initiated and organized by Microsoft. It is quite interesting that Microsoft has joined Oasis at the same time. Different from IBM, HP, Microsoft just turns in 100 thousand US dollars as annual fee. As the spokesman of Microsoft is quoted, all depends on the development of Oasis. That means that, if the standards formulated by Oasis are against the application of Microsoft, a war about the standards will be unavoidable.

XML is a meta-markup language. “Meta-markup” means that the developer can define his own tags according to his own needs. For example, one can define tags such as <book> or <name>. Any name that conforms to the naming rule of XML can be used as tags, which provides an access to different applications. Html is a predefined markup language, which cannot identify the user-defined tags but such predefined tags as <html>, <p>. Moreover, XML is a semantic/ structured language, which can describe the structure and semantics of documents.

From the above comparison we can tell that the XML documents have definite semantic and structures. XML is a universal data format. From the fundamental point of view, XML is a simple data format and 100% ASCII text, different from compressed data or Java objects which will not be readable once a single datum is corrupted. From an advanced point of view, it is a self-described language. XML can be used in data exchange primarily because the information represented by XML is platform-independent. Here the platform may refer to programs as well as operating systems. It has described a kind of regulation, with which the word documents of Microsoft can exchange information with Acrobat and databases.

For large and complex documents, XML is an ideal language. It allows designating the vocabulary in documents and the relationship between elements. For instance, it can be prescribed that an author element must have a name sub-element, or the business should include sub-business.

XML documents are composed of DTD and XML documents. DTD (Document Type Definition) is a set of grammar rules for tags, which indicates how the XML text should be organized. For instance, DTD can represent that a <book> should have a sub tag <author>, with or without sub tag <pages>. Of course, a simple XML document may not have DTD.

Although the XML Schema has imposed restrictions to the use of tags, the automatic processing of XML needs more strict and comprehensive tools. For example, DTD cannot guaranteed that a certain attribute of a tag should not be negative, so there comes the XML Schema. Since XML Schema itself is a formal XML document, the information exchange between it and other XML can be realized with the same tool. The initial XML Schema is proposed by Microsoft. Then after plenty of discussion and argumentation, the experts of W3C published

a requirements definition in Feb. 1999, indicating the requirements that scheme must conform to. And in May of the same year, the definition of schema came out. Currently, the XML revolver can work according to DTD or XML schema.

DOM realizes the content of XML as an object model, which simply represents

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how the applications access XML documents. DOM Level 1 of W3C defines how to realize the attributes, methods and events.

XSLT (XML Style sheet Language Transformation) is a language used to transform between XML documents. To put it simply, since different developers use different XML documents according to different applications, XSLT enables us to extract the data we need from a pre-defined XML document to construct the different forms such as XML, html and various scripts.

Framework is a high-level control of structure. With XML framework, the logic of business can be set apart so as to achieve the segregation of data from computation. Now the well-known frameworks include Biztalk of Microsoft, EBXML co-published by UN/CEFACT and Oasis in 1999. It is believed that there will be many frameworks soon. Of course, the development of XML has promoted many new technologies, including RDF and Xform. But for the most of them, W3C only proposes suggestions without formal standards. Some contents are still under discussion.

2.1.4 Java

Java language, which came into being in 1991, was initially named OAK language. It is a general environment designed by SUN for some digital products. The initial goal is to develop a software technology that is independent of platform. Before the appearance of network, OAK is unknown to the public. However, the network changed the fate of OAK.

Before the emergence of Java, the information on the Internet is made up of some dull html documents. It became unbearable to those who are absorbed in web surfing. They are eager to see some interactive content on the web. At the same time, developers hope to bring out some applications with high security, which are independent of hardware platforms. As to these requirements, the traditional programming languages appear helpless. The engineers in SUN subtly perceived this point. They began to apply the OAK technology to the web since 1994, and then developed the first version of HotJava.

Java is a simple, object-oriented, distributed, interpretative, robust, neutral, transplantable and multi-thread language. There are different editions for development environment of Java, such as Java Developers Kit of SUN, or JDK for short. Subsequently, Microsoft released Microsoft Visual J++, which, VJ++ for short, supports Java norm. Java has the following features:

1. Platform-independent

Platform independence means that Java can run on different platforms. Java has introduced the principle of virtual machine. JVM, established on hardware and operating system, implements the interpretation of Java binary code and provides interface for different platforms.

Introduction to E-commerce

2. Security

The programming of Java is similar to C++. C++ users can quickly master its essence. Java abandons the direct memory access mechanism of C++, and the memory is allocated by operating system when the program is running, which avoids the virus intruding the system via pointers. Java also provides security management for programs, which can avoid illegal access to programs.

3. Object-oriented

Java has adopted the object-oriented concept, which encapsulates the data into classes, and thus accomplishes the simplicity and low maintenance of programs. The encapsulation and inheritance of class enable the code to be reused by being compiled only once. The programmer just needs to concentrate on the design and application of the classes and interfaces. Java provides plenty of general object classes, and users can use the methods of parent class via inheritance. In Java, one sub class belongs to only one parent class. The inheritance relationship between object class and the subclasses provided by Java seems like a tree posed upside-down, the root of which is Object class. Object class with strong functions and its subclasses are commonly used.

4. Distributed

Java is built on the extended TCP/IP network platform. The library functions provide methods transferring and receiving information through http and ftp, which enables the programmer to use the online files as easily as the local files.

5. Robust

Java concentrates on checking errors during compilation and running time. Validation of Class helps to reveal many early errors. Java manipulates the memory by itself, which reduces the memory errors. Java also implements real array and avoids data overlapping. These functions greatly facilitate the development of Java applications.

Java provides all the functions of a powerful language, without any confusion. C++ has poor security feature, however, C and C++ are widely accepted. So Java is like C++, which makes it easy for users to learn. Java gets rid of many features of C++, which makes it highly refined. Java is also added with many useful features, such as garbage collection. Java has abandoned the following functions of C or C++: pointer, structure, Typedefs and #define, memory release. These modifications reduce general errors by 50%. Moreover, Java is small, the interpreter needs only 215K memory to run; it is more object-oriented and stronger in certain aspects than C++. Java processes data using object interfaces.

Nowadays, e-commerce is a popular topic. However, traditional programming languages are not sufficient for e-commerce systems. The features of Java, such as high security, excellent reliability, platform-independence, simplicity and object-orientation, have made it the principal language for implementation of e-commerce systems.

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