Trends in Web Servers_PHP Tutorial-PHP Tutorial-php.cn

(Authors: Cao Wenlong, Li Weisen) Currently, there are three main trends in the development of Web servers: 1. From HTML to XML (Extensible Markup Language - Extensible Markup Language) HTML is called the "first-generation Web language". As introduced earlier, HTML, as the development language of the Web, plays a key role in the development of Web applications. But HTML has a fatal shortcoming: it is only suitable for communication between humans and computers, not for communication between computers. HTML defines the presentation of document content through a large number of tags. It only describes how text and graphics should be arranged on a Web browser page. It does not describe the meaning of information on the Internet itself, and information is the most important in Web applications. content. The text and graphic content expressed through HTML are easy to be understood by humans, but are not conducive to understanding by computer programs. In addition, another problem with HTML is that its tag set is fixed, and users cannot add tags according to their own needs; and the specifications of various browsers are different. To ensure that the web pages we make using HTML can be used normally by all browsers, As shown, we can only create web pages using markup specified by the W3C (World Wide Web Consortium). As mentioned before, the information provided by the web server to the web browser comes from a database with a certain structure. In the database, for the convenience of retrieval and management, the information is based on its own meaning (such as name, age, work unit, etc.) are stored in the corresponding fields. Once these data are retrieved and converted into HTML through CGI, ASP, JSP, PHP, etc., their original meaning cannot be transferred to HTML tags, and users cannot follow the original meaning of the information. Go read. Moreover, due to different operating systems and databases, it is quite difficult for different systems and application levels to understand each other's data formats. This requires a new technology or standard that can share the original data structure originally saved in the database server at different system levels. This new technology is XML. Using XML can solve the above problems. W3C describes XML as follows: "XML describes a class of data objects called XML documents and partially describes the behavior of computer programs that process them. XML is an application instance of SGML. Structurally, XML documents Comply with SGML document standards. "Like HTML, XML is also a text-based markup language, both developed from SGML (Standard Generalize Markup Language). The difference between the two is that XML allows us to To express the document, you can freely define tags to express the document content with practical meaning. For example, we can define tags with practical meaning such as and name>. And XML does not have a fixed set of tags like HTML. It is actually a language that defines a language. That is to say, users who use XML can define endless tags to describe any data elements in the document and organize the content of the document into Rich and complete information system. To sum up, XML has four major characteristics: easy-to-storage data format, scalability, highly structured and convenient network transmission. These characteristics provide us with a brand-new way to create open, efficient, scalable and personalized Web applications. starting point. 2. From wired to wireless e-commerce is moving from desktops to a wider range of wireless devices, and Cahners In-Stat market analysts predict that the number of wireless users worldwide will increase from 271 million in 2000 to 13 in 2004. 100 million. Darcy Fowkes, research director of Aberdeen Group, believes that the advantage of using wireless e-commerce is not only convenience, it can also save the company's financial resources, and mobile office can make work more efficient. However, due to the complexity of the coexistence of multiple wireless network types, markup languages, protocols, and wireless devices, it is not easy to convert network content and data into a format that can be recognized by wireless devices. Currently, many companies are working on developing products that can extend applications and Internet content to wireless devices. For example, IBM's new version of WebSphere Transcoding Publisher 3.5 adds and improves many new features and can translate data on the corporate intranet to a variety of wireless devices. New features in this version include support for more wireless devices, data formats, and language translation capabilities. It is based on Java architecture and can convert applications and data written in markup languages such as HTML and XML into formats that can be recognized by wireless devices such as WML, HDML (Handheld Device Markup Language) and iMode, so that they can be accessed through handheld devices Information on the Internet. Wireless equipment manufacturer Mobilize has also launched Mobilize Commerce products to help enterprises enter wireless networks. The software can access the company's internal system through wireless connections, remotely send orders, and confirm them. Mobilize Commerce takes full advantage of XML to convert information into formats suitable for wireless devices, including laptops, personal digital assistants, wireless phones, Internet phones, and two-way paging. 3. From Silent to Sound There are now one billion telephone terminals in the world and more than 200 million mobile phones.As far as people's own communication habits are concerned, people are more willing to use oral methods of listening and speaking to communicate. At present, the research work of text to speech converter (TTS, Text to Speech) has made great progress, realizing automatic language analysis and understanding, and allowing TTS users to add more rhythm and tones in speech, so that The sound produced by the TTS system is closer to the human voice. In the field of automatic speech recognition systems (ASR), automatic speech recognition systems are developing from imitation matching of entire words to phoneme-level recognition systems. The vocabulary of automatic speech recognition systems consists of an alphabet based on sound segments, and this vocabulary is language-specific. Based on this method, speech can be found and picked out by the recognition system in a wide array of sounds and recognized. Moreover, when recognizing a word, each phoneme will be selected from the input of the system, and after splicing and combination, it will be compared with existing phoneme and word templates to generate the required template. Phoneme recognition greatly reduces the dependence of ASR on the speaker and makes it very easy to build large and easily modified speech recognition dictionaries to meet the needs of different application markets. Another aspect of the development of Web voice is the progress of VoiceXML (Voice Extensible Markup Language). The main goal of VoiceXML is to make interactive voice interfaces available for all the existing applications and rich content on the Web. The Web server processes a request from a client application. This request is processed by the VoiceXML interpreter and the VoiceXML interpreter context. In response, the server generates a VoiceXML file, and in the reply, it is processed by the VoiceXML interpreter. The VoiceXML 1.0 specification is based on XML and provides an intelligent API for voice and telephony application developers, service providers and device manufacturers. The standardization of VoiceXML will simplify the creation of personalized interfaces with voice response services on the Web, enabling people to access information and services on the website through voice and phone calls, retrieve central databases as they do today through CGI scripts, access corporate intranets, and create new of voice access devices. The VoiceXML execution platform is loaded with corresponding software and hardware, such as ASR and TTS, to realize speech recognition and conversion between text and speech. On May 23, 2000, the W3C accepted the Voice Extensible Markup Language VoiceXML 1.0 as an instance. At present, famous manufacturers such as IBM, Nokia, Lucent, and Motorola have developed corresponding products that support VoiceXML, but most of the current ASR and TTS systems cannot support Chinese.