World Wide WebWAN, also known asweb, which is based onHypertextandHTTPGlobal, dynamic and interactiveCross platformDistributed graphic information system based on gis.It is a kind of Internet basednetwork service, which provides a graphical and easily accessible intuitive interface for the browser to find and browse information on the InternetHyperlinkOrganize the information nodes on the Internet into an interrelatedReticular structure。[1]
Chinese name
Global Wide Area Network or World Wide Web
Foreign name
web
Alias
web
Full name
World Wide Web
Form of expression
Hypertext, Hypermedia, Hypertext Transfer Protocol
1989CERN（European Institute for Particle Physics）The team led by Tim Berners Lee in submitted a new protocol for the Internet and afile systemThe team named the new system World Wide Web, which aims to enable scientists around the world to use the Internet to exchange their work documents.
This new system is designed to allow any user on the Internet to search and obtain documents from the databases of many document service computers.At the end of 1990, the basic framework of the new system had been developed and implemented in a computer in CERN. In 1991, the system was transplanted to other computersComputer platform, and officially released.[2]
Form of expression
Announce
edit
IHyper text
Hypertext is a kind of userInterface modeTo display text and text related content.Nowadays, hypertext is generallyElectronic documentsThe text in the text contains information that can be linked to other fields or documentshyperlink, allow from the current reading positionDirect switchingTo the text that the hypertext link points to.
Hypermedia indoor effect picture class
There are many formats of hypertext, the most commonly used isHypertext Markup Language(Hyper Text Markup Language, HTML) andRich Text Format(Rich Text Format, RTF). The links on the pages we browse everyday belong to hypertext[5]。
hyperlinkA global information structure that links different parts of a document through keywords, enabling information to be searched interactively.
Hypermedia is short for hypermedia.yesHypertext(hypertext) and multimedia in the information browsing environment.Users can not only jump from one text to another, but also activate a sound, display a graph, and even play an animation.
The Internet uses hypertext and hypermediaInformation organizationTo extend information links to the entire Internet.Web is a kind of hypertext information system. One of the main concepts of Web is hypertext links.It makes the text no longer fixed and linear like a book, but can jump from one position to another and get more information from it, and can also go to other topics.If you want to know the content of a topic, just click on the topic to jump to the document containing the topic.It is this multi connectivity that calls it the Web.
IIIHypertext Transfer Protocol（HTTP, HyperText Transfer Protocol) is the most widely used one on the InternetNetwork Protocol。
characteristic
Announce
edit
Graphical
One of the most important reasons why the Web is very popular is that it can display colorful graphics and text on one page at the same time.Before the Web, the information on the Internet wasText form。The Web can provide the feature of integrating graphics, audio and video information.
Platform independent
Regardless of the user'ssystem platform You can access WWW through the Internet.There are no restrictions on the system platform when browsing WWW.Whether fromWindowsPlatform, UNIX platformMacWe can access WWW on platforms such as intosh.Access to WWW is through a method calledbrowser(browser).Such as Mozilla'sFirefox、GoogleOfChrome, Microsoft'sInternet ExplorerEtc.
Distributed
A large amount of graphics, audio and video information will occupy a considerabledisk spaceWe can't even predict the amount of information.For the Web, it is not necessary to put all the information together. The information can be placed on different sites. Just indicate the site in the browser.Physically, the information at a site is not necessarily logically integrated. From the perspective of users, the information is integrated.
Dynamic
Since the information of each Web site contains the information of the site itself, the information provider can oftenOn the stationInformation.Such as the development of an agreement, the company's advertising, etc.Generally, all information sites try to ensure that the informationTimeliness。Therefore, the information on the Web site is dynamic and frequently updated, which is guaranteed by the information provider.
Interactive
WebInteractivityFirst of all, itsHyperlinkThe user's browsing order and site are entirely up to him.In addition, dynamic information can be obtained from the server in the form of FORM.The user can submit a request to the server by filling in the FORM, and the server can return the corresponding information according to the user's request.
Webpage
Announce
edit
Brief description of the website
A web page is a page in a website, which is usually the basic element of a website and a platform for carrying various website applications.Generally speaking, a website is composed of web pages.
so-calledwebsite(Website) refers to the collection of relevant web pages on the Internet that are made by using HTML and other tools to display specific content according to certain rules.In short, the website is a communication tool, just like a bulletin board, people can publish or collect information through the website.
Constituent elements
Text and pictures are the two most basic elements of a web page.You can simply understand it as: words are the content of the web page, and pictures are the beauty of the web page.In addition, the elements of the web page include animation, music, programs, and so on.
Types of pages
Usually, the web pages we see are based on htm orhtmlFile ending with suffix, commonly known asHTML file。Different suffixes represent different types of web pages, such as CGI, ASPPHP、JSPEven more.
Classification of web pages
There are many categories of web pages. Our traditional classification is dynamic and static pages. In principleStatic pageMulti passWebsite DesignSoftware for redesign and change, relatively lagging, of course, there are websitesmanagement system, you can also generate static pages, which we call static pages.Dynamic pageadoptPage ScriptAutomatically process the automatically updated page with the language, for example, post it throughWeb serverRun program, automaticprocess information, update the web page according to the process.[1]
CGI is between external applications (CGI programs) and Web serversInterface standard, is the WWW serverRuntimeThe specification of external programs. Programs written according to CGI can expand the functions of the server and complete the work that the server itself cannot complete. The execution time of external programs can generate HTML documents and return the documents to the WWW server.CGI applications can communicate with browsersInteraction, you can also use the database API todatabase serveretc.External data sourceFor example, a CGI program can obtain data from the database server, format it into an HTML document, and send it to the browser, or put the data obtained from the browser into the database.Almost usedServer softwareAll support CGI. Developers can use any WWW server built-in language to write CGI, including popular C, C++VBAnd Delphi, etc.
fromArchitectureLooking up, the user enters query information through a web browser, and the browserHTTPThe protocol sends a request with query information to the Web server. The Web server activates the external CGI program according to the CGI protocol. The program sends a SQL request to the DBMS, converts the result into HTML, and returns it to the Web server.Then it is returned to the web browser by the web server.This structure reflectsClient/ServerWeb server and CGI program actually play the role of gateway for HTML and SQL conversion.The typical operation process of CGI is: analyzing CGI data;Open the connection with DBMS;Send SQL request and get the result;Convert the results into HTML;Close the connection to the DBMS;Returns HTML results to the Web server.
Web based database access utilizes existing information resources and servers.Its access frequency is high, especially for hot data.But its main disadvantages are: ① client and back-enddatabase serverCommunication must pass through the Web server, and the Web server needs to convert data and HTML documents. When multiple users send requests at the same time, information and publishing bottlenecks will inevitably form in the Web server. ②CGI applications need to open and close database connections every time they run, which is inefficient and time-consuming; ③CGI applications cannot have more than oneClientRequest sharing. Even if the CGI program is running when a new request arrives, another CGI application will start. As the number of parallel requests increases, more and more processes will be generated on the server.Generating processes for each request is time-consuming and requires a large amount of memory, which affects the efficiency of resource usage, leading to reduced and increased performancewaiting time；④Due to the great difference between SQL and HTML, the conversion code in CGI programs is tedious to write and difficult to maintain; ⑤Poor security, lack of usersaccess control , it is difficult to set security for the databaseAccess rights；⑥The HTTP protocol is stateless and has no frequent connections. The submission of DBMS transactions cannot be verified, and theOLTPApplication.
Expansion interface
In order to overcome the limitations of CGI, anothermiddleware The solution is based on the structure of the server extension API.Compared with CGI, API applications are more closely integrated with Web serverssystem resourceMuch less, andoperating efficiency However, it has been greatly improved, while providing better protection and security.
The server API is generally provided as a DLL and is the program code residing in the WWW server. Its function of extending the WWW server is the same as CGI.WWW developers can not only use APIs to solve all problems that CGI can solve, but also further solve special requests based on different WWW applications.Various APIs are closely combined with their corresponding WWW servers, and the running performance of the initial development target server is further explored and improved.The performance of programs developed with API is much higher than those developed with CGI, but developing API programs is much more complex than developing CGI programs.API applications need some programmingExpertise, such asMultithreading、Process Synchronization, direct protocol programming, anderror handlingEtc.The main WWW APIs are Microsoft'sISAPINSAPI of Netscape and WSAPI of OReily.Developed using ISAPIProgram performanceIt is better than programs developed with CGI, mainly because ISAPI applications areServer softwareIn the sameaddress spaceDLL, so allHTTP ServerThe process can directly use various resources, which obviously takes less system time than calling CGI program statements that are not in the same address space.The NSAPI, like ISAPI, customizes the basic services of the Netscape WWW server for WWW developers.Developers can use NSAPI to develop interfaces with WWW servers, anddatabase serveretc.External resourcesInterface.
Although the structure based on the server extension API can easily and flexibly implement various functions, it can connect all the 32-bit ODBCdatabase systemHowever, the defects of this structure are also obvious: ① between various APIscompatibilityVery poor, lack of unified standards to manage these interfaces; ②Developing API applications is also much more complex than developing CGI applications; ③These APIs can only work on dedicated Web servers and operating systems.
JDBC
JavaThe launch of, so that the WWW page has vitality and dynamic.Internet users can download Java from WWW serverAppletRun in your local browser.These downloaded applets, like local programs, can independently access local and other server resources.However, the original Java language did not have the function of database access. With the deepening of applications, the demand for Java to provide database access is increasing.In order to prevent different extensions to Java in terms of database access, JavaSoft has designated JDBC as the database access API of the Java language.
The advantage of using JDBC technology to access the database in Java Applet is that you can access the database directly and no longer needWeb DatabaseTo avoid some limitations of CGI method;useraccess control Can be set bydatabase serverLocal security mechanism to improve security;JDBC is a general low-level that supports basic SQL functionsApplication Program Interface, providing a unifieduser interface, cross platformdatabase systemDirect Web access provides a solution.Thus, some defects of API method are overcome;At the same time, it can easily interact with users, and provide rich graphics functions and multimedia information functions such as voice and video.
JDBC is Java for executing SQL statementsApplication Program InterfaceAPI，It consists of classes and interfaces written in the Java language.Java is an object-oriented, multithreaded andPlatform independentOfprograming language, with extremely strongPortability, security and robustness.JDBC is a specification that can provide developers with standard database access classes and interfaces, and can easilyrelational databaseSend SQL statements. At the same time, JDBC is a low-level application program interface that supports basic SQL functions, but it actually supports high-level database access tools and APIs.All this work is based on the X/Open SQL CLI.The main task of JDBC is to define a natural Java interface to connect with the abstraction layer and concepts defined in the X/Open CLI.The two main interfaces of JDBC are JDBC API for application developers and JDBC API forDriverLow level JDBC Driver API.JDBC completes the following tasks: establishing a connection with the database;Send SQL statement;Return the data results to the Web browser.
be based onJDBCOfWeb DatabaseThe defect of the structure is that it can only carry out simple database query and other operations, and cannot carry out OLTP;Security, buffer mechanism and connection management are still imperfect;SUNPromised cross platformdatabase systemThe functions and standards of are far from being realized.
Version introduction
Announce
edit
Web 1.0
The earliest network concept originated from the ENQUIRE project built by Tim Berners Lee in 1980, which is aHypertextAlthough the online editing database looks different from the Internet currently used, it is consistent in many core ideas.The era of Web 1.0 began in 1994, and its main feature is the massive use of staticHTMLWeb pages are used to publish information, and browsers are used to obtain information. At this time, it is mainly one-wayinformation transfer。Through the Web World Wide Web, resources on the Internet can be represented intuitively in a web page, and resources can be linked freely on the web page.The essence of Web 1.0 is aggregation, federation and search. The objects of aggregation areMassive, unorderednetwork information。Web1.0 only addresses people's needs for information search and aggregation, but does not address the needs for communication, interaction and participation between people, so Web2.0 came into being[4]。
Web 2.0
Web 2.0 began with a brainstorming meeting between O'Reilly Media and MediaLive International in March 2004.Tim O'Reilly summarized the concept of Web2.0 in the article "What Is Web2.0", and gave theblock diagram——Web2.0 MemeMap, this article has become a classic article of Web2.0 research.After that, the following articles on Web 2.0Related researchWith the rapid development of applications, the concept of Web2.0 andRelated technologiesThe growing maturity and development have promoted the reform and application innovation of the Internet.In Web 2.0, software is regarded as a service, and the Internet has evolved from a series of websites to a matureend userprovidenetwork applicationThe service platform that emphasizes user participation, online network collaboration, networking of data storage, social network, RSS application and file sharing has become the main support and expression of the development of Web 2.0.The Web2.0 model has greatly stimulated the initiative of creation and innovation, making the Internet vibrant again.Typical applications of Web 2.0 include BlogWiki、RSS、Tag、SNS、P2P、IMetc.[4]。
(1) Web2.0 pays more attention toInteractivity。Not only do users realizeNetwork serverIt also realizes the interaction between different users of the same website and the information interaction between different websites.
(2) Website design that conforms to web standards.Web standards are being promoted internationallyWebsite StandardsWeb standards generally refer toWebsite constructionThe website design language based on XHTML language is adopted. In fact, web standards are not a certain standard, but a collection of standards.TypicalApplication modeIt is "CSS+XHTML", abandoning the table positioning method in HTML4.0. One of its advantages isWebsite DesignCode specification, and reduce a lot of codenetwork bandwidth Resource waste, speeding up website access.More importantly, websites that conform to web standardsSearch EnginesMore friendly.
(3) There is no absolute boundary between web2.0 websites and web1.0.Web2.0 technology can become a tool for web1.0 websites. Some websites born before the concept of web2.0 also have web2.0 features, such asB2B e-commerce websiteFree of chargeInformation DeliveryandNetwork CommunityThe content of similar websites also comes from users.
(4) The core of web2.0 is not technology but guiding ideology.Web2.0 has some typical technologies, but technology is a means to achieve a certain purpose.Web2.0 technology itself is not the core of web2.0 website, the important thing is that typical web2.0 technology reflects the application mode with web2.0 characteristics.Therefore, web2.0 is not so much aInternet technologyThe innovation of Internet application is more like a revolution in the guiding ideology of Internet application.
(5) Web2.0 is a concept of the Internetideological systemUpgrading from the original top-down by a few resource controllerscentralized controlThe dominant Internet system has been transformed into a bottom-up system with usersCollective wisdomAnd power led Internet system.
(6) Web2.0 reflects interaction, readability and writability, and reflects various aspectsmicro-blog, photo album, more user participation.
Web 3.0
Web3.0 is the inevitable trend of the development of Intranet and the further development and extension of Web2.0.On the basis of Web 2.0, Web 3.0 willMicro contentContinue to split the smallest unit, standardize and structure the meaning of words, and realizeWeChatInteraction between and semantic based links between micro content.Web3.0 can further mine information and enable it to communicate directly from the underlying database.And put all kinds ofInformation pointAnd users' demand points are aggregated and dockedmetadataSo that the machine can understand the content of the web page, thus providing semantic based retrieval and matching, and making the user's retrieval more personalized, accurate and intelligent.The definition of web3.0 is that the information in the website can directly interact with the relevant information of other websites, and can integrate the information of multiple websites through the third-party information platform;Users have direct data on the Internet and can use it on different websites;Completely based on the Web, you can use a browser to realize the functions only possessed by complex system programs.Web3.0 browser will regard the network as a large-scale query that can meet any query requirementsInformation base。The essence of Web3.0 is deep participation, life experience and the value of Internet users' participation.
Technical Features of Web 3.0
(1) Intelligent and personalized search engine.
(2) Free integration and effective aggregation of data.
From the perspective of user participation: Web 1.0 is characterized by static and one-way reading, and users are only passive participants;Web 2.0 is characterized by sharingReal time network, users can achieve interactive participation, but this interaction is still limited;Web3. o is characterized by networking and personalization, which can provide more AI services and enable users to participate in real-time.
From a technical perspective, Web 1.0 depends ondynamic html And static HTML web page technology;Web2.0 uses BlogTAG、SNS、RSS、Wiki、Six degree separation, XML, AJAX and other technologies and theories;The technical characteristics of Web3.0 are comprehensive. Semantic Web and ontology are the implementation of Web3.0key technology 。
From the perspective of application: traditional portals such asSina、Sohu、NeteaseAnd so on are representatives of Web1.0;Blog Chinaxiaonei 、Facebook、YouTubeAnd so on are representatives of Web2.0;iGoogle、Broadland Network is the representative of Web3.0.[4]
Software and hardware platform
Announce
edit
Most Web servers are optimized for one operating system, so when selecting a Web server, it needs to be considered in connection with the operating system.IIS (Internet Information Server) isMicrosoftWindows2000/The Web server provided with NT hasAffinity, and inherits the consistentuser interface。Therefore, we adopt the following Web platforms:
(1) Hardware: server (PII300 or above, 128MB or aboveRAM, 100 Mbit/s NIC),Client(PII200+64 MB RAM, 100Mbit/s NIC);
(2) Software: server（Windows 2000/(NT Server 4.0) Chinese version, Server Pack 5.0 or above is recommended, IIS 4.0), client (Microsoft Win 9X Chinese version, IE 4.0 or above browser);
(3) Network: 100Mbit/s Ethernet is recommended.
social influence
Announce
edit
webSo that people all over the world can communicate with each other on an unprecedented scale.People far away, even people of different ages, can develop close relationships or make each otherideological levelGet sublimation, and even change their attitude and spirit towards small things.Emotional experience, political views, cultural habitsExpression, business advice, art, photography and literature can all be realized with low investment never seen in human historydata sharing。Although the use of the World Wide Web still depends on its own flawed materialized tools, at least its information preservation method is not the use of familiar ways such as libraries and publications.thereforeInformation disseminationVia the World Wide Web andInternetIt can be realized without being limited by the handling of specific books, or manual or physical reproduction.And the advantage of digital storage is that you can easily and efficiently query the information resources on the network than you can consult the library or real books.
