Glossary -- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

NDLP Glossary - H

halftone

A printed version of a "black-and-white" photograph or other art in which shades of gray are represented as patterns of black dots--the familiar form of picture reproduction found in newspapers and magazines. Traditionally, the technique to produce a halftone has involved photographing an original color or grayscale image through a screen with a grid.

Handle

One implementation of the concept of a Uniform Resource Name (URN) and a system to support URNs is the Handle System, developed by CNRI.

HTML

HyperText Markup Language. The markup language that is the basis for the World Wide Web. The success of the WWW is largely due to the initial choice of a very simple markup structure. Documents could easily be marked up (tagged) by hand, and browsers that could display the marked up documents attractively were easy to develop. Now that the WWW is widely used, there is demand for more powerful markup features. The development of HTML, especially specification and standardization, is coordinated by the World Wide Web (W3) Consortium.

HTML 2.0 is supported by recent versions of most browsers. Its features include forms that can be filled in, for instance to specify a search query. HTML 2.0 (and later versions are defined as an application of SGML (Standard Generalized Markup Language), with a formal DTD (Document Type Definition).

Work on defining and standardizing version 3.0 of HTML has been under way for some time. One important feature of the proposed version 3.0 of HTML is support for tables, which provides much more control over displaying search results. Many browsers already support tables, and it is likely that HTML 2.0 supplemented by support for tables will be adopted as an international standard by ISO.

It is not clear that version 3.0 of HTML will become a formal standard. While details have been discussed, commercial developers of WWW browsers (primarily Netscape and Microsoft) are adding their own features to the HTML language, hoping that these additions will become a de facto standard and supported by all browsers. Recently, a proposal has been made for a version 3.2 which incorporates some of the features introduced by the commercial developers.

Other key components of the World Wide Web are HTTP (HyperText Transfer Protocol) and URLs (Uniform Resource Locators).

HTTP

HyperText Transfer Protocol, the client/server protocol that is the basis for the World Wide Web. The popularity of the WWW is largely due to the simplicity of the protocol. The fundamental function of the protocol is for the client to issue a request to GET a resource identified by a particular Uniform Resource Locator (URL). The host server identified in the URL returns the requested information -- or sends an error message if the URL is not valid.

Glossary -- A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

NDLP Documentation: Intro -- Index

NDLP Glossary - H

Comments: (10/10/96)