532 GlossaryGlossary
Web Design in a Nutshell, eMatter Editionppi
Pixels per inch; the measurement of the resolution of a screen image.
QuickTime
A system extension that makes it possible to view audio and video informa-
tion on a computer. It was originally developed for the Macintosh but is now
available for Windows machines as well, and has been adopted as the video
standard by the ISO in their development of MPEG-4. The term also refers to
the file format.
RDF
Resource Description Framework; an XML application used to define the
structure of metadata for documents, i.e., data that is useful for indexing, navi-
gating, and searching a site.
resource fork
Extra code added in the Macintosh file format, which is used for storing icons,
previews, and file type information. This information should be stripped out
when sending the file to a non-Macintosh server. See alsodata fork.
RGB color
A color system that describes colors based on combinations of red, green, and
blue light.
rollover
The act of passing the mouse pointer over an element’s space, or the events
triggered by that action (such as a changing graphic or pop-up message,
sometimes called rollover events).
sampling rate
In a digital audio file, the number of samples taken per second.
server
A networked computer that provides some kind of service or information.
Server Side Includes (SSI)
Special placeholders in an HTML document that the server is to replace with
actual data just before sending the final document to the browser. Extended
SSI (XSSI) (part of Apache 1.2 and higher) provides more advanced command
functions, including conditional behaviors.
SGML
Standard Generalized Markup Language; a meta-language that provides a
comprehensive set of syntax rules for marking up the structure of documents
and data. HTML is a subset of SGML.
Shockwave
Proprietary technology from Macromedia, Inc. for the web delivery of multi-
media content.
spatial compression
In video, spatial compression is applied to each individual frame of the video,
using compression schemes commonly used on still images (also called
“intraframe” compression).