Mobile phone Development Combat 85--xml Introduction 1

Introduction to XML

XML (extensible Markup Language) extends the markup language, which, like HTML, is SGML (Standard generalized Markup Language, the standardized universal Markup language). XML is a cross-platform, content-dependent technology in an Internet environment, and is a powerful tool for the current processing of structured document information. Extensible Markup Language XML is a simple data storage language that uses a series of simple tags to describe data that can be built in a convenient way, although XML occupies more space than binary data, but XML is extremely simple and easy to master and use.

Unlike databases such as access,oracle and SQL Server, the database provides more powerful data storage and analysis capabilities, such as data indexing, sorting, lookups, correlation consistency, and so on, where XML is just the presentation of data. In fact, the biggest difference between XML and other data representations is that he is extremely simple. This is a seemingly trivial advantage, but it is this that makes XML different.

The difference between XML and HTML is that XML is used to store data in the data itself. While HTML is used to define data, the display mode of the data is heavy.

The simplicity of XML makes it easy to read and write data in any application, which makes XML quickly the only common language for data exchange, although different applications support other data interchange formats, but soon they will support XML, which means that programs can be easier with Windows, Mac OS, Linux and other platforms generated by the combination of information, and then can easily load XML data into the program and analyze him, and output the results in XML format.

In order to make SGML look user-friendly, XML redefined some of the internal values and parameters of SGML, removing a lot of the less-used features that make SGML complex when designing a Web site. XML preserves the structured functionality of SGML, which allows web designers to define their own document types, and XML also introduces a new type of document that allows developers to avoid having to define document types.

Because XML is a world wide, the standardization of XML is handled by the XML Working group, which is composed of experts from various places and industries who communicate their views on the XML standards and present their views (www.w3.org/TR/WD-xml). Because XML is a public format (it doesn't belong to any company), you don't have to worry about XML technology becoming a profitable tool for a handful of companies, and XML is not a specific browser-dependent language

XML English explanation

　　The Extensible Markup Language (XML) is a general-purpose specification for creating custom Markup languages. It is classified as a extensible language, because it allows the user to define the mark-up elements. XML ' s purpose is to aid information systems in sharing structured data, especially via the Internet, to encode documents, and to serialize data; In the last context, it compares with text-based serialization languages such as JSON and YAML. XML began as a simplified subset of the standard generalized Markup Language (SGML), meant to is readable by people via SE mantic constraints; Application languages can is implemented in XML. These include Xhtml,rss, MathML, GraphML, Scalable Vector Graphics, MusicXML, and others. Moreover, XML is sometimes used as the specification language for such application languages. XML is recommended by the world Wide Web Consortium. It's a fee-free open standard. The recommendation specifies lexical grammar and parsing requirements.

XML History

XML was a prototype from the 1996, and was proposed to the World Wide Information Network (XML1.0), which was released in 19,982 months as the standard for the web. XML, formerly known as SGML (the standard generalized Markup Language), is a standardized name from the GML (generalized Markup Language) that IBM has been developing since the 60.

　　Key Concepts of GML:

The document can be clearly separated from the content, and all documents are used in the same way.

In 1978, ANSI compiled the GML specification, published it as ISO 8879 for the sgml,1986 year, and is widely used in large file plans, but SGML is a very rigorous document description method, Lead to too large and complex (the standard manual has more than 500 pages), difficult to understand and learn, and thus affect its promotion and application.

As a result, SGML has been simplified to derive HTML. HTML is simple, there is no way to define the appearance of the document in the beginning, only to display the Web page file in the browser. Then, with the development of the Internet, people in order to control their file style, expanded the description of how to visualize the data of the label. After the browser battle between Netscape and Microsoft, the HTML standard authority has been sorely tested, fortunately, by the time HTML 4.0, the world of the web has regained its status.

　　also the issue of HTML is recognized by the consortium:

does not solve all the problem of interpreting the data-like the content of audio-visual files or chemical formulas, musical symbols and other patterns.

Performance issues-you need to download the entire file to start searching for files.

Scalability, elasticity, legibility are poor.

To solve these problems, experts use SGML to streamline production, and in accordance with the development experience of HTML, produce a set of strict rules, but simple description data language: XML. XML is born in a context where it is possible to have a more neutral way of letting the consumer decide how to digest and present the information provided by the * * *.

The purpose of XML is to provide a mechanism for the precise description of the information to compensate for the too-expressive nature of HTML.