Henrik Frystyk, July 1994 The official description of the World-Wide Web (WWW, W3) is a "wide-area hypermedia information retrieval initiative aiming to give universal access to a large universe of documents". It is a way of viewing all the on-line information available on the Internet as a seamless, browsable continuum. This section introduces the general concept of the World-Wide Web and the basic elements in the model. The content of the section is as follows:
Basic World-Wide Web ModelThe basic idea behind the World-Wide Web is based on a client server application and hypertext documents as illustrated in the figure below. The model is simplified in that it only contains elements that exists within the World-Wide Web concept. Later the model will be expanded to a generic resource accessing model. Show
Universal Resource IdentifiesIn order to address a data object or more general, a resource, in the model above it is necessary to define a name space that not only contains information about hosts but also about resources available on each host. The World-Wide Web model defines Uniform Resource Identifiers or URIs that specifies a syntax for encoding the names and addresses of data objects on the Internet and how they can be accessed. The set of URIs coversHypertext Transfer ProtocolThe Hypertext Transport Protocol (HTTP) is a generic stateless presentation layer protocol with elements from other Internet presentation layer protocols. The HTTP protocol is built on a client-server model where the client initiates a request and the server replies with a response.The basic format of the HTTP protocol is based on the MIME Protocol with a set of HTTP Headers possibly followed by a message body containing a data object in any 7-bit or 8-bit accepted by the client. The client specifies what data format it can handle by having a list of accept headers in the request. The basic WWW-model indicates that the client initiates a request and the server responds by sending a data object to the client. However, often the client wants to post a data object to the server, e.g. to post a mail message to an email address, to a news group, or to create a new file on the remote server. The HTTP protocol provides two methods for the client to transfer a data object to the server. Though, the client is not guaranteed that the request can be fulfilled - even on a successful return code. The action can at all times be cancelled by the responsible person of the remote server. One of the characteristics of the HTTP protocol is that it is a superset of the other Presentation Layer supported by the WWW-model. This means that messages generated by other protocols can be handled by the HTTP protocol by wrapping a set of HTTP/MIME headers around the message. This is an essential feature for the concept of Proxy servers. The current version 1.0 of the HTTP protocol is built on top of the TCP Protocol that is a connection oriented protocol with a 3 way handshake connection establishment. This causes an substantial overhead in a client-server oriented environment like the HTTP protocol. It would therefore be an excessive optimization if the HTTP protocol was moved to a lighter Transport Layer protocol such as the Transactional TCP Protocol which still provides a reliable stream transport service. Hypertext Markup LanguageThe Hypertext Markup language (HTML) is the users interface to create information on the World-Wide Web. The description of the World-Wide Web has until now focused on the technology that due to specifications and conventions provide the functionality necessary to request and serve information across the Internet. HTML is defined to be the hypertext language of communication which actually flows over the network. There is no requirement that files are stored in HTML. Servers may store files in any other formats and then generate a HTML on the fly upon a client request. This gives the possibility of having virtual documents instead of static documents on rapidly changing information like weather reports etc. HTML can be used to represent:
HTML is now superseeded by HTML+ that is an enriched DTD with possibilities of handling tables, math, images etc. Currently many browsers support a subset of the HTML+ specifications in addition to the basic HTML features. Interactive World-Wide Web ModelThe description of the Universal Resource Identifiers, the Hypertext Transfer Protocol, and the Hypertext Markup Language now calls for an update of the Basic WWW-model as illustrated in the figure.This model is a generic resource exchange model based on a client-server concept. Instead of the limited model with data flowing only from the server to the client, the client is capable of posting data to the server if the server allows this kind of service. Furthermore, the format of the data transferred in the message body can have any format from 7-bit ASCII text to 8-bit binary data. The transfer carrier can be any protocol supported by the World-Wide Web but the main protocol is HTTP as it can be used to encapsulate the other protocols supported, even a FTP message that is a highly state dependent protocol. Henrik Frystyk, July 1994 Which of the following explains the relationship between the Internet and World Wide Web?Which of the following best describes the relationship between the World Wide Web and the Internet? The World Wide Web is a system of linked pages, programs, and files that is accessed via a network called the Internet.
What is the relationship between the Internet and the World Wide Web quizlet?-The internet is a public, globally connected network of computer networks. -The web is a graphical user interface to information stored on computers running web servers connected to the internet. The web is a subset of the internet.
What is the relationship between the Internet and the World Wide Web Choose 1 answer?The Internet is a global network of networks while the Web, also referred formally as World Wide Web (www) is a collection of information that is accessed via the Internet.
Which of the following acronyms describes the technology used in newer flat screen computer monitors?Cards
|