Introductory Lectures on XML technology (1)

Xml

XML (extensible Markup Language, extensible Subscript language) is a standard published in February 1998 by the world's Wide Webconsortium, the Internet Consortium, Same as HTML is a simplified subset of SGML (Standard generalized markuplanguage, Standard Universal Markup Language). Because it combines the rich features of SGML with the ease of use of HTML in the Web application, since its inception, the rapid access to software developers and developers of the love of the program, showing a strong vitality.


Because XML solves the problem that HTML can't express data content, it has been widely used in government, finance, securities, post and telecommunications, insurance, taxation, judicature, publishing and electronic commerce.


Introductory Lectures on XML technology


XML vs. html comparison
Internet provides a global network interconnection and communication functions, the development of web technology is rapid, and its rich information resources to people's learning and life has brought great convenience. In particular, the emergence of HTML (Hypertext Markup Language), simple and easy to learn, flexible general features, so that people publish, retrieve, exchange information have become very simple, so that the web has become the largest global information resource database. However, the full rise of web-based emerging fields such as electronic commerce, electronic publishing and distance education makes the traditional Web resources more complicated and diversified, and the data volume is more and more large, which demands higher transmission ability of the network. At the same time, people's demand for Web services functions has reached a higher standard, for example: users need to intelligently semantic search of the web and the data according to different needs for the diversification of the display of personalized services; companies and enterprises to create and distribute a large number of valuable documentation information for customers to reduce production costs, As well as data integration and data transformation for different platforms, different formats of data sources, these needs are becoming more and more widespread and urgent.
Traditional HTML can not solve these problems effectively because of its limitation: as a simple expressive language, it can only display content and cannot express data content. This is precisely the E-commerce, intelligent search engine necessary. In addition, the HTML language can not describe the vector graphics, mathematical formulas, chemical symbols and other special objects, in the data display of the description of the ability is not satisfactory. Most importantly: HTML is only an instantiated subset of SGML (standardgeneralized markuplanguage, standard generic Markup Language), which is poor scalability, and users simply cannot customize meaningful labeling for others to use. All this has become a barrier to the further development of web technology.
SGML is a common document structure descriptor language, which provides an exceptionally powerful tool for grammatical labeling and is extremely extensible, so it is useful in data classification and indexing. However, SGML is too complex to be used for the day-to-day use of the network, coupled with the high cost of development, not supported by mainstream browsers, and so on, the spread of SGML on the web is hampered. In this case, it is imperative to develop a language that combines the power, scalability, and simplicity of HTML with SGML. Thus the XML language was born.
XML (extensible markuplanguage, extensible Subscript language) is a standard published by the Consortium in February 1998. It is also a simplified subset of SGML, which combines the richness of SGML with the ease of use of HTML in Web applications, defines the data structure in an open self-describing way, and highlights the description of the structure while describing the content, thus reflecting the relationship between the data. This organizes the data to be friendly and operable for both the application and the user.
Advantages and disadvantages of XML
One of the advantages of XML is that it allows organizations and individuals to build a set of sets that fit their needs, and they can be quickly put into use. This feature enables XML to be used in E-commerce, government documents, judicial, publishing, CAD/CAM, insurance agencies, manufacturers and intermediary organizations in the field of information exchange, for different systems, vendors to provide unique independent solutions.
The biggest advantage of XML is that its data storage format is not constrained by the display format. In general, a document consists of three elements: data, structure, and presentation. For HTML, the display is embedded in the data, so that when you create text, always consider the output format, if the same content for different styles of display when the requirements are different, to create a new document from scratch, duplication of work is heavy. Furthermore, HTML lacks a description of the data structure, which is inconvenient for the application to understand the content of the document and extract the semantic information.
XML separates the three elements of the document and processes them separately. First, separate the display format from the data content and save it in the style sheet file (StyleSheet) so that if you need to change the way the document is displayed, just modify the style sheet file. The self-describing nature of XML can well represent many complex data relationships, enabling xml-based applications to search for relevant data content accurately and efficiently in XML files, ignoring other unrelated parts. XML has many other advantages, such as it facilitates the exchange of information between different systems, can act as an Internet language, and is expected to become a standard mechanism for data and document exchange.
Of course, XML as a new set of standards, there are many deficiencies: it emphasizes the data structure, while the semantic expression ability is slightly insufficient, such as the definition of < address > Such a subscript, if not in the document to actually define the content, We cannot know whether to express the home address or the e-mail address. In addition, some of the XML technology has not yet formed a unified standard, fully supporting the application of XML is very small, even the browser's support for XML is limited.
Therefore, XML can not completely replace the HTML, after all, HTML is the most convenient and efficient way to publish online information. Moreover, HTML is the language that describes the display of data, and XML is the language that describes the data and its structure, and the two are functionally different.
The future of XML usage
In any case, the application of the web will be more exciting with the development of XML:
1. Business Automation Processing
XML's rich labeling can fully describe different types of documents, such as letters of credit, insurance policies, claims, and various invoices. The data that is sent to the Web by structured XML documents can be encrypted and easily appended with a digital signature. Therefore, XML has the hope to promote the large-scale application of EDI (Electronicdata Interchange) technology in the field of electronic commerce. Interested readers can visit the website http://www.xmledi.org.
2. Information release
Information release plays an important role in the competitive development of enterprises. The server only needs to issue an XML file, and customers can choose and produce different applications to process the data according to their own needs. With the help of the XSL (Extensiblestylesheet Language), extensive, general-purpose distributed computing is possible.
3. Intelligent Web applications and data integration
XML can more accurately express the true content of information, its strict syntax reduces the burden of the application, but also makes the development of intelligent tools more convenient. Data from different applications can also be translated into the unified framework of XML for interaction, transformation, and further processing.
The advantage of XML is very noticeable, its development is in the ascendant, the future web will be the web! of XML
Development tools FOR XML
There are many tools available for developing XML:
Notepad: The most direct and simplest text editing tool is available in Windows attachments.
Microsoft XML Notepad: Microsoft's editing software, designed specifically for XML documents, enables it to verify the validity of XML documents, detailing and downloading addresses: http://msdn.microsoft.com/xml/NOTEPAD/intro.asp.
Visual InterDev: The software is designed to develop Web applications, not just XML, but also ASP, HTML, XSL style sheets, and so on.
Microsoft XML tree Viewer: This software enables you to display the contents of an XML document in the form of a structure: http://msdn.microsoft.com/xml/demos/default.asp.
Microsoft XML Validator: The software can check whether the XML document is "well-formed" and its validity, and warns of errors, its download address is: http://msdn.microsoft.com/xml/demos/default.asp.
Microsoft XSL Debugger: The complexity of the style sheet files makes it easy for developers to write errors that help users debug style sheet files, displaying complex, tedious debugging processes with a visual interface. Download Address: http://msdn.microsoft.com/xml/_archive/xsl-debugger/xsl-debugger.htm.
WordPerfect: A text processor that provides advanced support for developing XML and SGML, has WYSIWYG development environments, provides wizards, automated control inserts, and automated document generation, and is a fee-based commercial product that supports windows95/98/ 2000 and Linux platform. Please visit http://www.corel.com/for more information.
Sixpack: Provides a concise interface for XML parsing and development, supports the Macintosh platform, and exposes source code, please visit http://www.trafficstudio.com/sixpack/info.htm for details.
Xray: An XML editor with real-time error checking. Based on DTDs or XmlSchema, it allows users to create well-formed XML documents or validate the validity of documents, and supports multiple-document editing, a freeware software that supports windows95/98/nt/2000 platforms. Please visit http://architag.com/xray/for more information. -->