This document represents an effort on the part of the W3C Web Characterization Activity to establish a shared understanding of key Web concepts. The primary goal in preparing this document was to develop a common interpretation for terminology related to Web characterization research. However, it is hoped that the Web community at large will also benefit from the enumeration and definition of important Web concepts.
Information on the W3C Web Characterization Activity is located at "http://www.w3.org/WCA/". A list of current W3C Recommendations and other technical documents can be found at "http://www.w3.org/TR/".
In this context we use them to describe the information space known as the Web. However, in addition to illustrating the scope of the Web in general, the reason why we mention them here is that they are needed to define a more restrictive set of terms used in Web characterization research which we can measure and define a set of metrics for.
The URI specification describes a resource as the common term for "...anything that has identity. Familiar examples include an electronic document, an image, a service (e.g., "today's weather report for Los Angeles"), as well as a collection of other resources. Not all resources are network "retrievable"; e.g., human beings, corporations, and bound books in a library can also be considered resources..." (see also the term Web Resource).
Examples: Web page, collection of Web pages, service that provides information from a database, e-mail message, Java classes ...
The URI specification defines a Uniform Resource Identifier (URI) as a compact string of characters for identifying an abstract or physical resource.
Note: For historical reasons, HTTP/1.x calls a manifestation for an "entity".
Examples: real-time information accessed from a news Web site on a particular day, up-to-the-minute stock quotes, a rendering of a multimedia Web page accessed with a particular client ...
A link expresses one or more (explicit or implicit) relationships between two or more resources.
Note: The type of the relationship can describe relationships like "authored by", "embedded", etc. Types can themselves be identified by URIs as for example is the case for RDF.
Examples: An HTML <a
href="http://www.w3.org/Protocols/#News">...</a> element,
an HTML <img src=<http://www.w3.org/icons/w3c-home">
element.
An area within a resource that can be the source or destination of zero, one or more links. An anchor may refer to the whole resource, particular parts of the resource, or to particular manifestations of the resource.
Examples: An HTML <a
name="http://www.w3.org/Protocols/#News">...</a>
element.
Examples: A Web browser, an e-mail reader, a Usenet reader ...
Examples: An HTTP server, a file server, etc ...
A proxy is an intermediary which acts as both a server and a client for the purpose of retrieving resources or resource manifestations on behalf of other clients. Clients using a proxy know the proxy is present and that it is an intermediary.
Examples: An HTTP firewall proxy ...
A gateway is an intermediary which acts as a server on behalf of some other server with the purpose of supplying resources or resource manifestations from that other server. Clients using a gateway know the gateway is present but does not know that it is an intermediary.
Examples: An HTTP to FTP gateway
Examples: A datagram sent from one Internet layer to another, an e-mail sent from one e-mail reader and received at another ...
Examples: HTTP GET, POST, PUT, and HEAD requests ...
Examples: An HTML document, a server error message ...
Examples: A person using a Web browser, a person using an e-mail reader, a person using a CRT terminal emulator ...
The principal responsible for the publication of a given resource and for the mapping between the resource and any of its resource manifestations. See also the term Web Site Publisher
Examples: A person writing an e-mail message, a person composing a Web page
The primitive elements defined above are useful when talking about the Web in general but are too broad in practice to enable us to characterize the Web with the desired level of rigor. This does not mean that we do not consider the general terms important or interesting, but that we need a mechanism for limiting the scope of the problem of characterizing the Web.
Therefore, we define the following terms to address the question of "What is the Web?" from the perspective of Web Characterization. For the purposes of Web Characterization research, the Web may be viewed as consisting of three components: the core, the neighborhood, and the periphery:
where
Notes: By the term "or its equivalent" we consider any version of HTTP that is currently implemented as well as any new standards which may replace HTTP (HTTP-NG, for example). Also, we include any protocol stack including HTTP at any level, for example HTTP running over SSL.
A resource, identified by a URI, that is a member of the Web Core.
Note: The URI identifying the Web Resource does not itself have to be found within the Web Core. That is, a URI written on a bus identifying a resource that is a member of the Web Core identifies a Web Resource.
A resource manifestation generated by a Web resource.
The collection of resources directly linked from a Web resource.
Examples: An "ftp" link within an HTML
document which can be accessed via HTTP, a "mailto" link within
an HTML document which can be accessed via HTTP.
The collection of resources on the Web which is not part of the Web Core or the Web Neighborhood.
Concepts relating to the process of accessing Web resources and render Web resource manifestations.
Examples: A Web browser, a harvester, a spider ...
A Web request is a request issued by a Web client. A Web request can be described as either:
and as either:
Examples: a) A user follows a link appearing in a HTML document (explicit, embedded Web request). The Web client retrieves the requested HTML document, and also makes an additional request for an image referenced in the HTML document (implicit, embedded Web request); b) A user reads the URI printed on a bus and feeds it to the Web client (explicit, user-input Web request).
The request header contains information about the request, information about the client itself, and potentially information about any resource manifestation included in the request.
Examples: Sample HTTP request header
The request body (if any) of an HTTP request is used to carry the payload of the HTTP message.
Example: At a library, a patron sits down at a public Internet-access terminal, accesses one or more Web resources, then relinquishes control of the terminal to another patron.
Example: Continuing the previous example, the library patron accesses a weather report (episode 1), checks stock prices (episode 2), then downloads a patch for his operating system (episode 3).
A Web response is a response issued by a Web server.
Examples: Sample HTTP Response Header
A collection of user clicks to a single Web server during a user session. Also called a visit.
Example: When the Web site of an online retail store is accessed for the first time by a particular client, a unique hashcode is sent back to the client to be stored locally. Then, when the client requests URLs from the site, the hashcode is appended to the URL request, allowing the Web site administrators to track the surfing pattern of the customer through the site.
Examples: An image file, an applet, and an HTML file identified and accessed through a single URI, and rendered simultaneously by a Web client.
Note: The components of a Web page can reside at different network locations. The location of the Web page, however, is determined by the URI identifying the page.
Note: The scope of a Web page is limited to the collection of Web resources which are displayed simultaneously by requesting the Web page's URI. The components of a Web page actually rendered in a page view is client-dependent.
Examples: Displaying a particular Web page in Internet Explorer is a pageview; displaying the same page in Netscape Navigator is a different page view.
<authority>
component but where the <path> component is either empty or
simply consists of a single "/" only.
Examples: The Web pages identified by
http://www.w3.org and http://www.cern.ch are host
pages
Examples: The Web page consisting of the
article "Thought Paper on Automatic Recharacterization" is part of the W3C Web site, since it satisfies the two
properties mentioned above. First, it resides at the same network location as
the W3C host page,
http://www.w3.org. Second, we can begin at the
W3C host page (http://www.w3.org) and follow a
sequence of internal links, ending at the article: specifically:
http://www.w3.org to http://www.w3.org/WCA/,
and
http://www.w3.org/WCA/ to
http://www.w3.org/WCA/1998/12/aut_char.html
Notes: It is not uncommon for Web sites to be duplicated, or mirrored, on multiple physical host machines (e.g., for load balancing purposes). Typically, it is immaterial to the client (or user) which host machine is used to access the Web site. In this case, it may be useful to consider this collection of "physical" Web sites, located at multiple host machines, as one "logical" Web site. This is possible in the case where a single domain name is mapped to each of the host machines; the logical Web site can then be identified using the unique domain name. If there is no unique domain name that can be applied to the collection of duplicate sites, we consider each physical host machine as a separate Web site.
Examples: If a page is mounted on a Web server, but is not linked to by any page on the Web site associated with the server, then the page is like an "island" on the Web. The only way the page can be accessed is through explicit knowledge of its URI.
Examples: The W3C is the publisher of the site located at http://www.w3.org/ ...
Examples: An Internet service provider supplying hosting services to its customers. All of the customers' Web sites may be located at the same IP address, but nevertheless represent logically independent sites (and, in the case of virtual hosting, may even have distinct domain names).
Examples: Web journal, electronic monograph, photo gallery ...
Examples: The resources available from a particular entity may be distributed over multiple servers, but users access the supersite through one host page, and view the distributed resources as one logical site.
Other useful places to look for terminology sections are
@(#) $Id: 01.html,v 1.47 2017/10/02 10:21:40 denis Exp $