Glossary

This chapter defines many of the terms commonly heard when talking about the Web.

ActiveX
ActiveX controls are programs that can be referred to in various types of documents and applications under Microsoft Windows, including HTML documents. These programs perform some action in the browser window. OLE is the mechanism under Windows by which ActiveX controls can communicate with a browser. Not all browsers support this feature. See also Java.
anchor
  1. An element in an HTML document that points to one of:
    • another document
    • a specific location in another document
    • a specific location in the current document
  2. An element that denotes a specific location in a document, pointed to by another anchor.
When the document is displayed in a browser, clicking on an anchor (of the first type) causes the browser to display the document and/or the location that it points to.
applet
See Java.
attribute
A value that is associated with an element but is not part of the content of the element (that is, text or sub-elements). For example, the URL part of an anchor is an attribute; you would use an attribute to specify the alignment of an image. In an HTML file, the attributes are actually located inside the element's start-tag, but when you're editing in HoTMetaL PRO, you view and edit attributes using the Element Attributes... command in the Markup menu.
browser
A networked program that communicates with Web servers, used for retrieving and displaying documents from the World Wide Web. Compare this with editor. Some well-known browsers are Mosaic, Netscape Navigator, Internet Explorer, Lynx, and Cello.
CERN
The European Laboratory for Particle Physics in Geneva, where the World Wide Web was `invented'. For more information, see http://www.cern.ch/.
CGI
An acronym for Common Gateway Interface. This is a feature of Web servers that allows HTML clients such as browsers to communicate over the Web with scripts installed on the server. HTML forms are often processed by such scripts. `CGI scripts' can be written in any programming language that will run on the server.
clickable image map
See image map.
client
A program, such as a browser, that uses HTML and communicates with a Web server.
client-side image map
See image map.
DNS
Domain Name System. This is the way in which the network turns a host or Internet domain (e.g., sq.com) into an Internet IP address for use with TCP/IP.
editor
A program, such as HoTMetaL PRO, used to create, or change the content of, HTML documents. Compare this with browser.
element
Elements are the structural building blocks of HTML documents. Blocks of text in HTML documents are surrounded by elements according to their function in the document: for example, headings, lists, paragraphs, and anchors are all surrounded by specific elements.
firewall
In networking, a firewall is a computer that prevents an intruder from accessing all the computers on a network if he or she manages to break into one computer someplace. The firewall usually sits between your inside network and the outside Internet. For more information, see Cheswick & Bellovin's approachable book Internet Firewalls: Repelling the Wily Hacker.
form
A group of elements (enclosed by a FORM element) in an HTML document, which generate graphical controls such as text entry boxes, radio buttons, and check boxes when the document is displayed in a browser. The user can enter information in a form and use the browser to submit it to a program on a Web server.
frames
Some browsers support special elements that let you divide the browser window into several sub-windows, called frames, each of them displaying a different document.
FTP
The File Transfer Protocol; one of the schemes that can be specified in a URL. This has traditionally been one of the most important of the network services. It lets you pick up a copy of a file from a remote computer, provided that you can connect to that computer (with TCP/IP, for example).
GIF
The unofficial standard graphics format used in HTML documents. This format is owned by CompuServe. See also PNG.
gopher
A line-mode Internet protocol that predates the Web. Web browsers can normally communicate with gopher servers.
home page
The top-level document on an organization's Web server, usually containing introductory information and links to other relevant pages.
hot image; hot spot; hot text
Hot text is text in a hypertext document (such as an HTML document) that is a link to some other file; a hot image is an image that is a link to some other file; a hot spot is hot text, or a region in an image map.
HTML
The HyperText Markup Language. This is the usual format for documents that are `published' on the Web. HTML is an application of SGML.
HTML browser
See browser.
HTTP
The HyperText Transfer Protocol. This is used to transfer HTML documents over the network, between a Web server and an HTML browser, while you wait. The HTTP protocol is implemented by a number of Web servers.
HTTP server
See Web server.
hypertext
Text that contains links to other documents. HTML documents are examples of hypertext.
ICADD
The International Committee for Accessible Document Design. Techniques created by ICADD and documented in ISO 12083 specify how to automatically transform SGML files (including HTML files) into input to a Braille, large print, or synthesized voice system. All HTML documents created by HoTMetaL PRO are ICADD-ready and can readily be converted to these formats using ICADD techniques.
IETF
The Internet Engineering Task Force, responsible for the technical management of the Internet. The IETF coordinates the development of the HTML standard.
image map; image map file
An image map is an image that is divided into regions, each of them associated with a URL. Clicking in a region causes the file referred to by the associated URL to be accessed. An image map is also called a clickable image map. There are two kinds of image maps: server-side (ISMAP) image maps require an external image map file that defines the regions in an image map and assigns them to URLs. Client-side (USEMAP) image maps accomplish the same thing using special elements in the document itself. Client-side image maps are easier to implement but are not supported by all browsers.
interlaced image
An image that is first displayed in the browser at a low resolution, and then in successively higher resolutions, until the whole image has been downloaded. This is sometimes referred to as progressive display. GIF, JPEG, PNG images can be interlaced. Not all browsers support this feature.
Internet Explorer
A popular browser developed by Microsoft Corporation.
Intranet
An `internal net', whose pages are available only on a local server. An organization can use Web technology, such as browsers, servers, and editors to share information among its members or employees, but not make this information accessible over the WWW.
ISMAP
See image map.
ISO
The International Organization for Standardization (`ISO' is not an exact acronym).
ISO 8859/1 character set
This is the character set for `special' or `accented' characters supported by HTML. This character set is also called `ISO Latin 1'. It includes characters required for most western European languages: Dutch, English, French, German, Italian, Irish, the `Iberian' languages, and the `Nordic' languages. This character set is one of several in the ISO 8859 standard: others support, for example, eastern European languages and Cyrillic-based languages. Only ISO 8859/1 is currently supported by HTML, however.
Java
Java is a programming environment that operates in conjunction with certain browsers. It lets you refer to and run programs, called applets, from an HTML document. Applets perform some special processing in the browser window, such as drawing a picture or interacting with the user. The Java programming language is a platform-independent object-oriented language, with some similarities to C and C++. See also ActiveX.
JavaScript
JavaScript is a programming language that is loosely based on Java. Instead of being referred to in an HTML document, as Java applets are, JavaScript code is embedded in the document itself, using the SCRIPT element.
JPEG
An image format that is commonly supported by Web browsers. JPEG is an acronym for Joint Photographic Expert Group.
line-mode browser
An HTML browser that can be used on a `dumb terminal' such as a VT100 or a PC with communications software. The most common are Lynx and a program called www from CERN.
link
See anchor.
Lynx
A common line-mode HTML browser. Lynx can be used over a dial-up line or if you don't have a windowing system.
mailto
A scheme that causes a browser to send a form to a particular e-mail address, or generate a mail-editing window.
markup
Special codes in a document that specify how parts of it are to be processed by an application. In a word-processor file, markup specifies how the text is to be formatted; in an HTML document, the markup specifies the text's structural function (heading, title, paragraph, etc.).
marquee
A piece of text that scrolls across a browser document window. This feature is implemented using the MARQUEE element. Not all browsers support marquees.
MIME
The Multipurpose Internet Mail Extensions (RFC 1510): extensions that allow e-mail messages to contain audio, video, and multiple files. It is also the format that Web servers and browsers use to transfer files. The MIME content type of a file tells a browser how to process it. The content type for HTML files is `text/html'.
Mosaic
One of the most widespread HTML browsers.
NCSA
The National Center for Supercomputing Applications, located at the University of Illinois at Urbana-Champaign, Illinois. The NCSA is an (indirectly) U.S. government-funded body that exists to try and make powerful computers more accessible to researchers. Mosaic was originally written at NCSA.
Netscape Navigator
A popular Web browser developed by Netscape Communications Corporation.
OLE
See ActiveX.
page
A single HTML document (which can be longer than one screen).
PNG
Portable Network Graphics; pronounced `ping'. A graphics format intended as a replacement for GIF, on account of patent infringements involving the compression algorithm used with GIF. PNG is a `lossless' format; some of its advantages over GIF are better (24-bit) color support, compression, and anti-aliasing and transparency capabilities.
progressive display
See interlaced image.
proxy server
If you have a firewall at your site, you can't normally connect directly to a server on the Internet. You need an agent, a proxy server running on the firewall, to make the connection for you. To you, inside the firewall, it pretends to be the server that you're attempting to connect to; on the outside, it pretends to be the client, and talks to the real server, thus letting you talk to a server outside the firewall (or vice versa).
relative URL
A URL that is missing some information (such as the scheme or network location), which a browser is expected to inherit from the URL of the document that contains the relative URL.
scheme
The part of a URL that tells an HTML client such as a browser how to retrieve the file specified in the URL. Also called `protocols'.
server
See Web server.
SGML
An international standard for describing the markup of structured documents. The basic idea behind SGML is that information can be made independent of particular hardware and software. This is done by storing all documents as text-only files (with references to documents in other formats, such as graphics, when required), and using markup that describes the structure of documents, rather than their physical appearance. SGML is described by the ISO 8879 standard (1986). HTML is an application (a particular instance) of SGML.
tag
An element in an HTML file begins with a start-tag (e.g., `<PRE>') and (usually) ends with an end-tag (e.g., </PRE>). In the HoTMetaL PRO display tags are represented by tag icons at the beginning and end of an element. Sometimes tags are called `commands', but this isn't correct.
TCP/IP
Transmission Control Protocol/Internet Protocol. This is the low-level protocol used by much of the Internet. It's really two protocols; IP packets are sent over a network that itself uses TCP. Other common variations include SLIP (pronounced `slip'; Serial Line/Internet Protocol), and PPP (Point to Point Protocol).
transparent image
An image that has had one color (usually the dominant background color) designated as `transparent', so that when the image is displayed in a browser, the image's background is colored with the browser's background color. The desired effect is an image that does not have a rectangular boundary.
URI
Uniform Resource Identifier. This is a generic name for any of a class of ways of identifying resources on the Internet. Three types of URIs are URCs (Uniform Resource Classification), URLs (see the next entry), and URNs (Uniform Resource Name). Implementations of URCs and URNs are still in an experimental stage. The basic idea is that a resource (e.g., a document) is identified by a URN, a kind of `public identifier' in the SGML sense. The URN is resolved into a URC, which is a collection of information about the resource (it could include, for example, the price of obtaining the resource, and one or more URLs).
URL
Uniform Resource Locator. A URL is the address of a file, written in a format that can be interpreted by a Web server, which then retrieves the file. A URL consists of a filename and, usually, a scheme that tells how the file is to be retrieved. For most files on Web servers, the scheme http is used.
USEMAP
See image maps.
W3C
The WWW Consortium. This has been set up at MIT, modelled after the X Consortium that promotes X Windows. W3C is a not-for-profit organization that provides sample code and co-ordinates standardization. For more information, see http://www.w3.org/.
Web, the
An informal name for the World Wide Web.
Web server
A networked program that responds to requests from local or remote computers for HTML files. You give the Web server a file name (in the form of a URL) and it gives you back the file (which can be in any format, text or binary) over the same network connection.
World Wide Web
This is a generic term for the collection of Web servers and browsers that literally spans the world. Usually abbreviated WWW.
WWW
The World Wide Web.