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Note: Boldface terms within entries are also defined in the glossary.
In some cases, separate terms (e.g., RGB and color model)
that are grouped consecutively (RGB color model) in the main
text and glossary may appear to be one term.
AAT (Art & Architecture Thesaurus)
A controlled vocabulary maintained by the Getty Research Institute
that identifies and organizes art and architecture terminology.
access file (or access image)
A file derived from a master file that is used to make a digital collection
item accessible without hazarding the master. Typically compressed
to reduce storage requirements and speed online delivery.
access points
A database field or metadata category designed to be
searchable and retrievable by an end-user. Also used to denote a
place where wireless network access is available.
ACL (Access Control List)
A way to limit access to networks to authorized users by using
a router to forward or block requests from users based on a given
protocol or criteria, such as IP address.
adaptive palette
A reduced palette of colors chosen to give the best possible
reproduction of an image when it is displayed in a limited or "palettized" color
environment, such as an 8-bit (256-color) display, or within a 256-color
image format, such as GIF.
AFRICOM (International Council of African Museums)
Body that originated as a program of the International Council of Museums (ICOM)
that has developed a metadata standard designed to promote the standardization
of museum collection inventories in Africa.
algorithm
A set of steps in a specific order, such as the instructions in a computer
program. Different image compression schemes employ different algorithms;
for instance, the JPEG algorithm processes images as 8 x 8 image-blocks
and applies cosine transformations to each block, while the JPEG2000 algorithm
applies wavelet transformations to the image as a whole.
analog
Any continually fluctuating or changing process, or any mechanism in which
data is represented by continuously variable quantities. Analog images are continuous
tone-the range of colors or shades of gray that they can include are
virtually unlimited, and therefore their colors graduate smoothly. Because
data in analog form can theoretically be represented by an infinite number
of values, it may be difficult to differentiate between accurate reproduction
and noise; thus, analog technology does not facilitate the accurate
creation of copies, and analog reproduction may be of lower quality than digital reproduction.
annotation
Commentary added to a media object, generally providing explanatory information
or editorial notes regarding the media file. Annotations are a form of metadata.
ANSI (American National Standards Institute)
U.S.-based body that does not directly develop standards but coordinates
and administers voluntary consensus standardization initiatives.
archival master
The raw, original image captured by the scanning process and/or an image created
and managed so as to optimize longevity and future usefulness. File naming, file
formatting, color space selection, capture resolution, and similar
specifications should be based on documented standards. Archival masters
may be used as the source for access images, or these may be created from derivative
masters. See digital preservation.
artifact
An error introduced into an image during capture or digitization, formatting, compression,
or other transformation processes. Most commonly used to refer to the perceptible
degradation of an image after a lossy compression schema has been used.
ASP (Active Server PageT)
One of several methods of dynamically generating Web pages in response
to user input that may be used to gather information from remote databases.
Utilizes "ActiveX" scripts. A Microsoft specification that may require third-party
software to run on non-Windows platforms. ASP may also indicate an Application
Service Provider. See CGI, JSP, PHP.
authentication
A human or machine process that verifies that an individual, computer, or information
object is who or what s/he or it purports to be. Used in allowing access
to secure systems.
authenticity
Refers to the trustworthiness of a digital entity, to its being what
it professes to be, as regards its identity, origin, history, authorship, integrity,
and/or the accuracy with which it documents an original work. The degree to
which authenticity can be ascertained or guaranteed is likely to be determined
by the quality of custody or management an entity enjoys over its life cycle.
authority (or authority file)
A file or set of terms extrinsic to records describing objects or documents.
A more efficient way of recording information, which need be recorded only
once and may then be linked to all appropriate records.
bandwidth
Denotes the capacity of a communications channel, such as an Internet link.
Determines how fast data can flow over the channel. See bit rate.
batch processing
The automated application of a given process, such as compression, to
multiple files.
bit
The smallest unit of computer data, denoted by a single binary value, either
0 or 1. Eight bits make up one byte in most computer systems.
bit depth
Also known as sample depth or color depth. The number of bits
used to describe the color value of each pixel in an image, which in
turn dictates the number of colors available to a given media file, monitor,
or other device. An 8-bit image has 256 possible colors. A 24-bit image has
approximately 16 million. See dynamic range.
bitmap (or bitmapped image, raster image)
An image made up of a given number of pixels, each with a specific color
value, laid out in a grid. Ideal for reproducing photographic representations,
because a sufficient quality and quantity of pixels can give the appearance
of a continuous tone image. Resizing will affect apparent image
quality. For instance, enlarging an image involves enlarging each pixel, which
entails a reduction in resolution. See vector graphic.
bit rate
The number of bits that pass a given point in a network in a
given amount of time, generally measured in kilobits or megabits per second
(Kbps or Mbps). The bit rate is a measure of bandwidth and may also
be referred to as the data transfer rate.
Boolean
A system of logical thought developed by George Boole (1815-1864) and adopted
for use with binary values of computer operations. In Boolean searching,
terms such as AND, OR, and NOT are used as operators to combine or exclude
search terms.
born digital
Creations originally generated in digital form rather than copies or
surrogates of analog originals, and which exist entirely in a digital
environment. Examples include software, Web pages, hypertext fiction,
and digital art.
broadband
High-speed data transmission or a transmission medium in which a wide range
or band of frequencies is available to transmit data, allowing more information
to be transmitted in a given time frame. As of this writing, broadband is
sometimes defined as services that offer bit rates of 1.544 megabits
per second (Mbps) and above. May also be referred to as wideband. Digital
Subscriber Lines (DSLs) and cable modems allow broadband transmission. See bandwidth.
browser
See Web browser.
browser-safe palette
A palette of 216 colors whose appearance is predictable in all browsers and
operating systems. Developed for 256-color displays-the remaining 40 colors
are rendered differently by Macintosh and IBM-compatible or Wintel operating
systems. Still used in Web design.
BSI (British Standards Institution)
Body that coordinates and publishes British, European, and international
best practice recommendations and standards.
byte
In most computer systems, a unit of data that is eight binary digits
or bits long. Generally used to represent a character such
as a letter or number but may also hold a string of bits needed in
some larger unit, such as the stream of bits that make up a visual
image.
CAD (Computer-Aided Design)
Software used in architecture, archaeology, design, and other fields to create
precision drawings, models, and technical illustrations in two or three dimensions.
See born digital, vector graphic.
calibration
The comparison of the specifications of image-capture, processing, or
display devices to a known standard to determine, and perhaps correct,
any deviation or error. See color management.
capture resolution
The number of samples per inch (spi) that a scanner or digital
camera is capable of capturing, or the number of samples per inch captured
when a particular image is digitized.
cataloguing
The process of creating and arranging records that describe materials so as
to facilitate identification, search and retrieval, acquisitions, circulation, preservation,
rights, evaluation, and collocation. A record generally consists of a description;
headings for topics, persons, places, etc.; an identification number; and
links to related resources, such as authority records. Differs from
a simple listing by the imposition of controlled vocabularies and
by mechanisms allowing users to draw relationships between various entities.
CBIR (Content-Based Information Retrieval)
Technology that is able to retrieve images on the basis of machine-recognizable
visual criteria. Such indexing is able to recognize and retrieve images
by criteria such as color, iconic shape, or by the position of elements within
the image frame.
CCD (Charge-Coupled Device)
Light-sensitive integrated circuits employed in image capture by scanners and digital
cameras. CCDs capture image data as pixels with a numerical value
that can be converted into an electrical charge, the intensity of which is
related to a particular color.
CCITT
The former Comité Consultatif Internationale de Télégraphique
et Téléphonique, now the ITU, that develops communications standards,
including a group of related lossless compression schemas for black-and-white
images used in fax transmission and supported by the PDF and PostScript language
file formats.
CD-ROM (Compact Disk, Read-Only Memory)
A type of write-once, read-many (WORM) disk used to store and distribute large
amounts of digital data on low-cost, optically recorded media. CD-ROMs
profess to have much longer storage life ratings than magnetic media
such as tape or hard disks, though there have been a few notable instances
of failure in less than five years. Gold-reflective-layer CDs are most recommended
for long-term storage. A standard CD-ROM stores approximately 650 megabytes
of data. See DVD-ROM.
CDWA (Categories for the Description of Works of Art)
A conceptual framework for describing and accessing information about artworks
and surrogates, maintained by the Getty Research Institute. The Visual Resources
Association (VRA) Data Standards Committee expanded upon certain portions
of the CDWA to formulate the VRA Core Categories.
CGI (Common Gateway Interface)
Part of the Web's Hypertext Transfer Protocol (HTTP). A platform-
independent method of dynamically generating Web pages in response to user
input that may be used to gather information from remote databases. See ASP, JSP, PHP.
channels
The separate color components used by various color models. By default, RGB images
have three channels: red, green, and blue; CMYK images have four: cyan,
magenta, yellow, and black. Extra or "alpha" channels can be added to describe,
for example, levels of transparency, or be used as masks that allow or restrict
the output of color. Color creation occurs when the channels are combined before
being sent to an output device such as a screen or printer.
checksum
A simple count of the total number of bits in a file or transmission
unit that may be used to assess data integrity or detect error. In digital
preservation management, checksums can be used to ascertain whether the
number of bits in a file has changed over time.
CIDOC (International Committee for Documentation)
A committee of the International Council of Museums (ICOM) involved in developing documentation
standards, such as the CIDOC Information Categories and CRM. See AFRICOM.
CIDOC Information Categories
A metadata standard intended to describe museum collection objects developed
by the International Committee for Documentation.
CIE (Commission Internationale de l'Eclairage)
Organization that has developed a number of device-independent color models collectively
called CIE color, including CIE XYZ, CIE LAB, and CIE LUV, that specify color
based on human perception and are used as the basis for color management
systems. See CMS, color profile.
client
See client/server.
client/server
Refers to a system architecture that divides functions between two or more
computers, or two or more programs, so that one program, the client, makes
a service request from another program, the server, which fulfills the request.
This architecture is seen in networks where a client program in one
computer (such as a Web browser) forwards a request to a server program
in another (possibly distantly located) computer, which returns information
to the client.
CMS (Color Management System)
A system designed to ensure the most accurate reproduction of color across
multiple input, output, and display devices, and through the life cycle of
an image. Each device in a color workflow will have inherent biases that
cause it to interpret digital color values differently, and no device
can properly reproduce the entire range of visible colors. Modern color management
systems employ ICC color profiles to describe the color reproduction
capabilities (and limitations) of individual devices. These are mapped to
a device-independent CIE-based color space, facilitating conversion
to matching color output across multiple devices and systems, within the
practical limits of the devices. CMS may also refer to Content or Collection
Management Systems.
CMYK (Cyan, Magenta, Yellow, Black)
Often referred to as four-color process, CMYK is a subtractive color model,
using a mix of cyan, magenta, yellow, and black inks to reproduce a range of
colors. CMYK is the most basic color process used in print.
codec
A compression/decompression (sometimes coder/decoder) algorithm or
scheme that reduces the volume of bits necessary to store a data object
such as an image file (compression) but that allows the reconstruction
of the compressed data into a usable format for display, processing, etc. (decompression).
There are many different codecs, and they are often used to minimize file transfer
time in order to optimize images or data for Web use.
color chart
A calibration target consisting of a matrix or spectrum of colors set
to a known standard. Color charts can provide reference points to ensure
accuracy of color capture and to calibrate output devices. May also be referred
to as a color patch. See gray scale.
color correction
The process of adjusting color values in an image to match the original or
a reference image in order to compensate for the normal shifts and biases
incurred during digitization and subsequent image processing. See CMS.
color depth
See bit depth.
color management
The practice of calibrating all devices in the image capture,
processing, and output chain to ensure the fidelity of digital image
files to the objects they represent. Color management can be achieved by manually
calibrating devices using color charts and ICC profiles followed
by regular reassessment, or by means of CMS software.
color model
An attempt to describe color in a mathematical, predictable, and reproducible
way. Usually posits a small core set of colors from which all possible colors
can be derived. The RGB model assumes that all colors are formed by
a given combination of red, green, and blue; the CMYK model assumes
that all colors are produced by a combination of cyan, magenta, yellow, and
black. Both models fall short of describing the whole gamut of visible color.
Also known as color system or color space. See CIE, gray
scale, HSB/HLS.
color profile
A file containing data that describes a particular device's color space in
relationship to an ideal, theoretical, device-independent color space (the CIE XYZ
color space). Profiles facilitate the conversion of images from one color space
to another and form the foundation of color management systems (CMS).
Most profiles are generated using ICC standards.
color space
A three-dimensional geometric representation of the colors that can be discerned
and/or created by a particular color model (the two expressions may
be used interchangeably). May also refer to the range of possible colors
that can be produced by a particular output device-such as a monitor, color
printer, photographic film, or printing press-or the color description abilities
of a particular file format; may also be known as a color gamut. Generally
described by a color profile.
compression
The reduction of file size to facilitate transmission or storage via
any of various algorithms. Often required by image files, which are
significantly larger than text files. Some algorithms allow the original data
to be reconstituted upon decoding or decompression (lossless compression),
while others discard data permanently (lossy compression), which allows
a greater reduction in file size. Regardless of the type of compression used,
the higher the level of compression, the more noticeable will be the loss in
image detail. See codec.
continuous tone
Refers to images that have an unlimited (or nearly so) range of colors or shades
of gray, and which show smooth gradation between shades. Digital image
reproduction is always confined to limited palettes, albeit palettes
that may have millions of different colors, while the ability of bitmapped
images to mimic continuous tone is limited by their bit depth and resolution. See analog, HDRI, pixel.
controlled vocabulary
An established list of terms from which an indexer or cataloguer may select
when assigning descriptors or subject headings to a record. See authority, cataloguing, indexing, thesaurus.
CRM (Conceptual Reference Model)
A metadata standard, developed by CIDOC, intended to provide
a common and extensible semantic framework to which any cultural heritage information
can be mapped.
cross-platform
Applications or data that can be used over more than one computer platform
or operating system. Facilitated by the adoption of open standards.
crosswalk
A chart or table that represents the semantic mapping of fields or data elements
in one metadata standard to fields or data elements in another standard
that has a similar function or meaning. Crosswalks allow semantic interoperability.
They enable heterogeneous databases to be searched simultaneously
with a single query as if they were a single database, and facilitate accurate
conversion from one metadata standard to another. Also known as field mapping
or metadata mapping. See RDF.
DAM (Digital Asset Management)
A system that enables the management of digital objects, such as image
files, from ingest to archiving and supports continued retrieval. Off-the-shelf
DAM software may offer templates and other devices or strategies to facilitate ingest, metadata capture,
and searching. May also be called media asset management (MAM).
database
A structured collection of data. The most common data-structuring model is "relational," where
data is organized in related or linked tables that can be accessed or reassembled
in many different ways. Object-oriented databases are also common.
data dictionary
An exhaustive list and description of data elements. May be contrasted with
a metadata schema, which is a selection of data elements and rules
for their use geared to a particular purpose.
DCMI (Dublin Core Metadata Initiative)
Body engaged in the development of interoperable online metadata standards to
support a broad range of purposes. See Dublin Core.
decompression
See compression.
derivative file
A file derived or created from another file, rather than created during an
original digitization process. Differs from a copy insofar as the derivative
file may be altered in some way from the original.
derivative master
A high-quality "working" image file that is derived from an archival master image
file, then subjected to some form of processing, such as color correction.
May also be known as a submaster. Typically used as the source from which smaller,
lower-quality access images intended for transmission over the Internet are
derived, while archival masters are kept reserved.
digital
Electronic technology that generates, stores, and transmits data in terms of
a limited number of discrete states, most commonly as binary data in which
two possible states, positive or nonpositive, are represented by 1 or 0,
respectively. Because there are only two possible values, the accuracy of
binary digital data at any given point is relatively easy to test, and therefore
digital technology facilitates the creation of accurate copies. See digital
image.
digital archaeology
The process of reclaiming digital information that has been damaged or is unusable
due to format or media obsolescence. May employ any number of techniques. See digital
preservation.
digital asset
See digital object.
digital camera
An image-capture device that directly captures digital images
without the use of film or other analog processing. Digital cameras
typically employ CCD photosensors and output bitmapped images. See drum
scanner, flatbed scanner, transparency scanner.
digital certificate
An electronic identifier issued by a certification agency that establishes
a user's credentials. Contains the registrant's name, a serial number, certificate
expiration information, a copy of the certificate holder's public key,
and the digital signature of the certificate-issuing authority. A
recipient can verify that a certificate is real by comparing the public key
received with that held in a registry for the certificate holder.
digital image
An image described as a set of digital data, such as pixels or
vectors. Digital images may be digitized from analog sources
such as photographs or may be generated directly within computer applications.
If they are not born digital, bitmapped images consist of pixels
whose values are derived from samples taken from analog originals, and
may use thousands or millions of discrete gradations of color to approximate
analog continuous tone images. See bitmap, vector graphic.
digital object
Data (the content or "essence" of a digital file) and the metadata describing
it, regarded together as a single entity. Also known as a digital asset, an
information object, or an information package. May also refer to born digital objects.
digital preservation
The specific problems and methods of preserving digital, as opposed
to analog, assets because of their vulnerability to format obsolescence
and media decay. Various strategies have been developed to respond to this,
including documentation, the gathering of preservation metadata,
the use of open standards, redundant storage, refreshing, migration, emulation, technology
preservation, re-creation, and digital archaeology.
digital signature
A form of electronic authentication of a digital document. Digital
signatures are created and verified using public-key encryption and
serve to tie the document being signed to the signer.
digitizing
The process of deriving digital objects from analog originals
by converting their sampled values to binary code. Also known as analog-to-digital
conversion and image capture.
DIN (Deutsches Institut für Normung)
National standards body that represents German interests at European
and international levels.
diodes
Light-sensitive electronic components used in image capture. They function
as one-way valves that sense the presence or absence of light and create a digital signal
that the computer converts into pixel values.
directory (or directory service)
A listing of users and user passwords linked to information about which network resources
each user may access. Examples include LDAP, Active Directory, and NDS.
DMZ (DeMilitarized Zone)
In the computer network context, a computer host or small network that
provides an intermediate space between an extranet and an intranet and
so prevents direct access to internal network resources by unauthorized users.
Typically secured by two or more firewalls.
documentation
Textual information that describes a work of art or image, recording its physical
characteristics and placing it in context. May be regarded as one of the
most basic preservation strategies for digital files. See cataloguing, digital
preservation, metadata.
domain name
An address that identifies an Internet or other network site
and acts as a mnemonic alias for an IP address. Domain names consist
of at least two parts: the top-level domain, which specifies host addresses
at a national or broad sectoral level (e.g., ".edu" for the U.S. educational
sector); and the subdomain, which is registered to a specific organization
or individual within that domain (e.g., "getty" is registered to the Getty
Trust within the .edu domain).
dot pitch
The distance between phosphor "dots," the smallest visual components of an
electronic display device. Dot pitch is measured in millimeters (mm) and indicates
how sharp a displayed image can be: the smaller the dot pitch, the sharper
the image. Users working with images will usually want 0.28mm or finer dot
pitch. See monitor resolution.
DRM (Digital Rights Management)
Server software that may use a number
of techniques to control distribution of (usually
commercial) content over the Web.
drum scanner
A high-quality image-capture device that uses PMT technology.
The original is secured to the drum surface with mounting tape and oil, and
the drum then revolves at several hundred revolutions per minute around the
scanning mechanism, which in turn moves along the drum, executing a tight spiral
scan of its entire surface. Capture resolution is determined by the
number of samples per revolution and the speed at which the scanning
sensor moves. Allows higher resolution, wider dynamic range,
and greater bit depth than flatbed scanners. See digital
camera, transparency scanner.
DTD (Document Type Definition)
A formal specification of the structural elements and markup definitions to
be used in encoding SGML-compliant documents. Examples of DTDs include EAD and HTML. XML is
a flexible format that allows for the creation of various DTDs to fit particular
purposes. See XSD.
Dublin Core
A minimal set of metadata elements that creators or cataloguers can
assign to information resources, regardless of the form of those resources,
which can then be used for network resource discovery, especially on
the World Wide Web.
DVD-ROM (Digital Versatile Disk, Read-Only Memory)
A type of write-once, read-many (WORM) disk used to store and distribute large
amounts of digital data on low-cost, optically recorded media. The
DVD-ROM is a newer, and more densely packed, form of storage than
the CD-ROM, and therefore not as well established or, possibly, as
reliable for archival purposes. A double-sided, dual layer disk can store
up to seventeen gigabytes of data, but the more densely packed the data is,
the more vulnerable it is likely to be to degradation. Gold-reflective-layer
DVDs are recommended for long-term storage.
dynamic range
The ratio between the brightest and darkest parts of an image, or the potential
range of color and luminosity values that can be represented within an image
or produced or recognized by a particular output or capture device. See bit
depth, color space, HDRI, palette.
EAD (Encoded Archival Description)
An SGML DTD that represents a highly structured way to create "finding
aids" for groupings of archival or manuscript materials, making them accessible
to researchers by listing the constituent items and their locations.
effective resolution
May be used misleadingly as a substitute term for interpolated resolution.
Generally refers to "real" resolution under given circumstances. Examples
include: the possible capture resolution of a digital camera,
as constrained by the area actually exposed by the camera lens; the number
of pixels per inch of an image, as affected by resizing that
image; or the capture resolution of a scan taken from an intermediary
such as a photograph, when mapped to the scale of the original object.
emulation
A digital preservation strategy that uses current software to simulate
original or obsolete computer environments. May either restore full functionality
to archival data or provide a simple viewing mechanism. See digital
archaeology.
encryption
A way of transforming data into "cyphertext" through the use of computer algorithms that
rearrange the data bits in digital signals in order to prevent
them from being read by unauthorized users. May also be used for user and document authentication,
because only designated users or recipients are given the capability to decrypt
or decipher encrypted materials.
extranet
A private network that allows an organization to share information,
such as parts of their intranet, with external users such as vendors
or clients over the Internet. Extranet systems require security such
as firewall server management and a means of user authentication.
failover
A backup operational mode in which functions are assumed by secondary system
components if the primary component becomes unavailable. Used to make storage and
other systems more fault-tolerant.
film scanner
See transparency scanner.
firewall
Software, or software and hardware, that serves as a gateway to block certain
types of network traffic, typically used to protect intranets from
access through extranets. Most firewalls work by filtering packets
and routing requests based upon IP addresses. Others use secure log-on
procedures and authentication certificates.
flatbed scanner
An image-capture device resembling a photocopy machine. The object to
be scanned is placed facedown on a glass plate, and a CCD array that
passes beneath the glass captures an image of the object by sampling it
at regular intervals. See digital camera, drum scanner, transparency
scanner.
format
A specification for organizing data. Digital images (and their associated metadata)
may be presented in a number of formats depending on compression schemes,
intended use, or interoperability requirements. Some image formats are
broadly decipherable, while others may only be accessible to certain application
programs. See GIF, JPEG, JPEG2000, PNG, TIFF.
FTP (File Transfer Protocol)
A method of moving, transferring, or copying files between computers over the Internet via TCP/IP,
rather than simply viewing them over the World Wide Web via HTTP with
the aid of a Web browser.
GIF (Graphics Interchange Format)
A widespread digital image file format introduced by CompuServe,
which supports basic animation capabilities and uses LZW compression.
Can provide only 8-bit color (256 colors) and employs an adaptive palette for
each image, making GIF undesirable for most continuous tone images,
such as photographs, though useful for limited-palette, monochrome,
or thumbnail images.
gray scale
The range of shades of gray that scanners and monitors can recognize
and reproduce, or that is contained within a black-and-white image. May also
be used as an alternative term for black and white (a black-and-white image
that is digitized has been "grayscaled"). Or, a calibration target showing
a standardized continuum of shades between black and white used to determine image-capture device
specifications. See color chart.
hacker
A term used to describe a person who endeavors to break into a computer system
for some purpose by circumventing security protocols. Sometimes used to describe
a particularly talented programmer.
HDRI (High-Dynamic Range Image/Imaging)
An image or image processing device that utilizes a greater dynamic range or
higher bit depth (generally 48-bit or higher) than can be shown on a
typical display device, or that can be captured by a single exposure with an
ordinary camera. The "extra" bits are used to record light and shade
(luminance) more accurately.
header
In a computer file, a field or series of fields that precedes the main file
content and contains metadata describing, for instance, the compression or
size of an image. Some such fields are automatically filled, but additional
metadata may be embedded into the header part of files of certain formats for
description and management purposes.
HSB/HLS (Hue, Saturation, Brightness/Hue, Lightness, Saturation)
Two variations of a device-independent color model that closely matches
the way the human eye perceives color. Often used in desktop graphics programs.
HTML (HyperText Markup Language)
An SGML-based markup language used to create documents for World
Wide Web applications. Predominately concerned with specifying the design
and appearance of content, rather than the representation of document structure
and data elements. See XML.
ICC (International Color Consortium)
Body promoting the standardization of open, vendor-neutral, cross-platform color
management system (CMS) architecture and components. Developer of the
ICC color profile specification.
ICONCLASS
A system of letters and numbers used to classify the iconography of works of
art, developed in the Netherlands.
IEC (International Electrotechnical Commission)
Organization that prepares and publishes international standards that
may serve as a basis for national standardization for all electrical, electronic,
and related technologies.
IEEE (Institute of Electrical and Electronics Engineers)
Body that promotes development and standards in the electronic and information
technologies and sciences.
image capture
See digitizing.
image resolution
The number of pixels, in both height and width, making up an image.
Generally, the higher the number of pixels, the greater the image's clarity
and definition. See resolution.
index
See indexing.
indexing
The process of making a list of terms and other data stored in a structured
data file and used to enhance access and discovery. Indexing terms represent
the most salient information necessary to retrieve a record or object; they
are often taken from a controlled vocabulary. See authority, cataloguing, thesaurus.
ingest
The process of entering new assets into a management system. The contributor
transmits an asset and its metadata, either bundled together as a
single digital object or separately, to allow accurate retrieval and
eventual reuse of the asset.
integration
Combining systems, applications, or sets of data so that they work together.
In "seamless" integration, the distinctions or boundaries between systems
are imperceptible to users.
integrity
A digital entity has integrity when it is whole and sound or when it
is complete and uncorrupted in all its essential respects. See authenticity.
interface
Allows users to communicate with, or use, applications by entering or requesting
data. Most are now graphical user interfaces (GUIs), in which functions are
displayed graphically and can be activated using a cursor or similar pointing
device rather than using older text-, keyboard-, or menu-driven controls.
Hardware interfaces allow pieces of equipment to communicate or work together.
Internet
A global collection of computer networks that exchange information by
the TCP/IP suite of networking protocols.
interoperability
The ability of different computer-based systems or applications to work together
correctly, particularly in the correct interpretation of data semantics,
or their ability to understand and, where appropriate, utilize each other's
data. Applications and systems that adhere to known standards promote
interoperability and remove reliance on a small group of suppliers.
interpolated resolution
The resolution at which a device is capable of capturing or generating
an image using interpolation (i.e., using data that has no authentic
relation to an original). See optical resolution.
interpolation
An estimation of a value within two known values. A means by which a device
can exceed its optical resolution capacity by inserting new pixels in
between those derived by sampling the original. Can improve apparent
picture quality; however, interpolated images tend to look blurred when they
are enlarged and use data that is inauthentic or not derived from the original.
intranet
A private network that is accessed via TCP/IP and other Internet protocols
but uses a gateway to limit access, typically to local users recognized by IP
address, domain, or by some other means of authentication.
IP (Intellectual Property)
Any intangible asset that is a product of human knowledge and ideas. Examples
include patents, copyrights, trademarks, and software. IP may also denote "Internet
Protocol."
IP (Internet Protocol)
The method by which data packages are delivered from computer to computer over
the Internet. Once delivered, the Transmission Control Protocol (TCP)
puts them into the correct order. IP may also denote "intellectual property."
IP address
Part of the Internet Protocol (IP). A hierarchical, numeric addressing
system that can be used to identify each device sending or receiving information
on a network with a 32-bit number.
ISO (International Organization for Standardization)
Body that promotes standardization. Many national standards-making bodies,
such as ANSI, participate in, and contribute to, ISO standards making.
The Joint Photographers Experts Group (JPEG) and the Motion Picture
Experts Group (MPEG) are both bodies within the ISO.
ITU (International Telecommunications Union)
Organization with the United Nations System that coordinates telecom networks and
services. The ITU-T division produces standards or recommendations for
all areas of telecommunication.
JFIF (JPEG File Interchange Format)
A public domain iteration of the JPEG image-compression format.
JPEG (Joint Photographers Experts Group)
A body within the ISO. Also a widely adopted image compression standard developed
by that body, which uses a lossy-compression algorithm able to significantly
reduce image file size while maintaining reasonable image quality. Typically
capable of compression ratios from 10:1 to 20:1.
JPEG2000
A file format that uses wavelet compression to allow both lossy and lossless
compression and can provide scalable images from a single compressed file.
Commercial implementations are becoming available, and open-source implementations
are in development. A separate standard to JPEG, and generally able
to provide reasonable image quality at higher compression ratios (some sources
cite ratios of 2:1 with lossless compression and up to 200:1 with lossy compression).
JSP (Java Server PagesT)
One of several methods of dynamically generating Web pages in response
to user input that may be used to gather information from remote databases.
Platform-independent technology developed by Sun Microsystems that utilizes
small programs called "servlets." See ASP, CGI, PHP.
LAN (Local Area Network)
A limited network, typically within a building or department and owned
and operated by the user. May be connected to other networks, such as the Internet,
via network points known as gateways. An ethernet is a high-bandwidth LAN
specification used to network computers and other devices together in a cabled
or wireless environment.
LCSH (Library of Congress Subject Headings)
A controlled vocabulary of terms commonly used to retrieve library materials.
lossless compression
Reduction in file size without loss of information, achieved by storing data
more efficiently. A bitmapped image that has undergone lossless compression
will be identical to the original uncompressed image when decompressed. The GIF, TIFF, PNG,
and JPEG2000 image formats allow lossless compression, which cannot
shrink file size to the extent possible with lossy compression.
lossy compression
Reduction in file size that involves permanent loss of information. Algorithms selectively
discard data in order to attain a greater size diminishment than is possible
with lossless compression. Entails a decrease in quality, but this is
often imperceptible (or nearly so) with image files, depending on the level
and type of compression employed. The JPEG and JPEG2000 formats allow
lossy compression.
LZW (Lempel-Ziv-Welch)
A proprietary lossless-compression algorithm.
machine-readable
Data presented in an electromagnetic form that a computer can access, such
as data stored on disk or tape, and organized in such a way that given the
correct program, a computer can process or execute instructions contained
in the data, such as rendering an image.
MAM (Media Asset Management)
A system for handling media assets through processes such as cataloguing,
controlling access, managing circulation, tracking rights and publication history,
and ensuring preservation, or software designed to perform all or some
of these tasks. May also be called digital asset management (DAM).
MAN (Metropolitan Area Network)
A network that connects users over a region larger than a LAN but
smaller than a WAN. Can be used to denote the interconnection of several
LANs but most often applies to the interconnection of networks in a city into
a single, larger network.
MARC (MAchine-Readable Cataloguing)
A set of standardized metadata structures that facilitates cooperative cataloguing and
data exchange in information systems. Developed to describe bibliographic materials
but extended to describe nonbibliographic holdings.
master file (or master image)
A high-quality, uncompressed digital file, or the highest quality file
available, from which other files, most commonly smaller, compressed files
for online access, can be derived. Master images will have the greatest
level of detail and color fidelity available. See archival master, derivative
master.
metadata
Commonly defined as "structured data about data," or data captured in specific
categories or elements. Metadata can include data associated with either an
information system or a data object or set of objects for purposes of description,
administration, preservation, the documentation of legal requirements,
technical functionality, use and usage, and so forth. See cataloguing, digital
object.
metadata schema
A set of rules for recording or encoding information that supports a specific metadata element
set.
meta tag
An HTML tag that enables descriptive metadata to be embedded
invisibly on Web pages, used by some search engines to establish
relevance to search requests.
METS (Metadata Encoding and Transmission Standard)
A flexible XML format for digital library objects that provides
a "wrapper" to hold together the various types of metadata that
may be used to describe an asset or group of assets. Data and metadata may
be embedded within a METS document, or the document may point to external resources.
The format's generalized framework offers a syntax for the transfer of digital
objects between repositories that may be used within the OAIS model.
middleware
A computer program that mediates between two existing, separate computer programs.
migration
Digital preservation strategy that involves
transferring data from a format or standard that
is in danger of becoming obsolete to a current format or standard.
The most common example is the process of upgrading
files to become compatible with a new version
of software or operating system. May also be
known as conversion or reformatting.
MIX (Metadata for Images in XML)
XML metadata schema developed by NISO and
the Library of Congress, based on the NISO
Data Dictionary: Technical Metadata for Digital
Still Images.
MODS (Metadata Object Description Schema)
XML metadata schema developed by the Library
of Congress and the MARC Standards Office
designed to both transmit selected data from
existing MARC 21 records and enable the creation
of original resource description records.
monitor resolution
May be used interchangeably with screen resolution or may indicate the
maximum possible resolution of a computer monitor. Higher monitor resolution
indicates that a monitor is capable of displaying finer and sharper detail,
or smaller pixels. Monitor detail capacity can also be indicated by dot
pitch.
MPEG (Motion Picture Experts Group)
A body within the ISO that has produced standards for the compression, storage,
and documentation of multimedia and motion pictures, such as the MPEG-7
standard or the MPEG-21 Multimedia Framework.
MPEG-7 (Multimedia Content Description Interface)
A metadata standard that provides a set of standardized tools to describe
multimedia content. Both human users and automatic systems that process audiovisual
information are within its scope.
NAF (Name Authority File)
Authority file maintained by the Library
of Congress that contains headings for names,
uniform titles, and series.
NAS (Network-Attached Storage)
A system where a data storage device is attached to a LAN and
assigned its own IP address, rather than being attached to the server offering
data processing and management functionality, thus releasing the server from
data delivery duties. May be incorporated into a SAN system. Affordable
consumer NAS systems are entering the market as of this writing.
native-XML
Used to describe applications that are able to process XML data without
transforming it to another format. For instance, native-XML databases allow
XML documents to be stored, indexed, and retrieved in their original format,
preserving their content, tags, attributes, entity references, and ordering. See XML-enabled.
nearline
Storage and retrieval system where assets
are stored offline, such as on removable
disks (hard drives, CD- or DVD-ROMs),
but are available in a relatively short time
frame if requested for online use or use
over a network.
network
An arrangement of devices such as servers, computers, and printers joined
by transmission paths by which programs make requests of one another. Local
area networks (LAN), metropolitan area networks (MAN), wide area
networks (WAN), and the Internet are all examples of networks.
network topology
A particular configuration used to connect devices on a network.
NISO (National Information Standards Organization)
Body that identifies, develops, maintains, and publishes technical standards to
manage information in both traditional and new technologies.
noise
Unwanted data or imperfections in a file that are somehow developed in the
course of scanning, processing, or data transfer.
OAI (Open Archives Initiative)
Body that develops and promotes interoperability standards that aim
to facilitate the efficient dissemination of content, such as its XML/Dublin
Core-based Protocol for Metadata Harvesting, which provides a mechanism
for "harvesting" or gathering XML-formatted metadata from diverse repositories.
OAIS (Open Archival Information System)
The Reference Model for an Open Archival Information
System provides a common conceptual framework
for creating archival systems designed to aid
the long-term preservation of, and access
to, digital information. Often cited in
concert with METS; a METS document could
serve as a Submission Information Package (SIP),
an Archival Information Package (AIP), or a Dissemination
Information Package (DIP) within the OAIS model.
Object ID
Metadata schema that sets out the minimum
information needed to protect or recover an object
from theft and illicit traffic. Its purpose is
to uniquely identify an object in order to establish
ownership.
offline
Storage and retrieval system where assets
are not immediately available for use, or not
accessible through a network or computer,
but stored on some independent media, such as
a CD-ROM.
online
Storage and retrieval system where assets
are immediately available for use or directly
connected to a network or computer through
fixed disk storage.
OPAC (Online Public Access Catalog)
Automated, computerized library catalogs made available to a wide range of
users.
open architecture
A system design and framework that is well defined and uses open standards so
that functionality can be added by third parties. This allows the original
technology to benefit from industry-wide developments and allows users more
flexibility in extending an application or building interoperability with
other systems.
open source
A product or system whose workings or source code are exposed to the public
and therefore to modification by anyone. Open source software is generally
developed as a public collaboration and made freely available for use or
modification as developers see fit, as opposed to proprietary products
or systems. Open systems built to known standards promote interoperability.
open standards
Freely available structures, procedures, or tools for the uniform creation
and description of data. Usually defined and perhaps maintained by a central
body, but, unlike proprietary standards, users are not reliant on
a private organization to license use and provide support.
optical resolution
The resolution at which a capture device, such as a scanner or digital
camera, is capable of capturing pixel values based on actual samples taken
from an original to construct an image. Optical resolution is the true measure
of the capture capacity or quality of a scanner, as opposed to interpolated
resolution.
output resolution
The resolution of an image based upon the dimensions, in pixels or
units of length, as affected by the chosen output method, such as display on
a monitor or printing on a page.
palette
The set of colors that appears in a particular digital image, or the
set of available colors based on the color space being used by a particular
output device.
password
A character sequence providing means of authentication for a user requesting
access to a computer or application. A password is typically entered along
with a user name or identifier that, when paired with the password, serves
to uniquely identify a user and associate the user with a particular profile,
or set of access privileges and rights.
peer-to-peer (P2P)
As distinct from client/server relationship, a peer-to-peer network connects
computers or programs so that no party is dedicated to serve the other, and
any is able to initiate a transaction.
PHP (Hypertext Preprocessor)
One of several methods of dynamically generating Web pages in response
to user input that may be used to gather information from remote databases.
Utilizes open source script language. See ASP, CGI, JSP.
pixel
From picture element. The smallest programmed unit of a bitmapped
image, similar to grain in a photograph or a dot in a halftone print. Pixel
size, frequency, and color determine the accuracy with which photographic images
can be represented. The greater a pixel's bit depth, the greater the
number of different shades or colors it can represent. The larger or fewer
the pixels within an image, the more likely "pixelation"-where individual pixels
become apparent and break the illusion of continuous tone-is to occur. See resolution, sample.
plug-in
An easily installed, usually downloadable program used by a Web browser to
enable the use of certain media or the execution of specialized Web functionality.
A media player, where audio or video encoding requires a particular player
to decode and run media files, is an example of a plug-in.
PMT (PhotoMultiplier Tube)
An amplifying vacuum tube used in drum scanners. PMT technology is highly
sensitive to differences in light intensity. It takes in light reflected from
reflective originals or through transparent originals, converts it to an electrical
signal, and amplifies the signal to measurable levels that can then be assigned digital color
values.
PNG (Portable Network Graphics)
A patent-free file format for lossless compression of images
that provides some additional features that improve the ability to control
image appearance over the GIF format.
preservation
See digital preservation.
printer resolution
The maximum density of dots per inch that a printing device is capable of producing,
or the density of dots per inch used in a particular printing.
proprietary
A technology or product that is owned exclusively by a single commercial entity
that keeps knowledge of its inner workings secret. Some proprietary products
can only function when used with other products of the same ownership. The
limitations of proprietary technology are fueling moves toward open standards.
public-key encryption
A security measure used in digital signatures wherein a value provided
by a designated authority is combined with a private key value and used to encrypt transmitted
data.
quality control
Techniques ensuring that accuracy and high quality are maintained through various
stages of a process. For example, quality control during image capture might
include comparing the scanned image to the original and then adjusting colors
or orientation.
RAID (Redundant Array of Independent Disks)
Storage device comprised of systems of
multiple hard disks holding the same information.
Intended to increase performance and reliability
in serving and storing data. There are various
RAID configurations, each suited to different
needs relating to demand or traffic, user needs
such as read-only or read/write, and fault-tolerance
requirements.
raster image
See bitmap.
RDF (Resource Description Framework)
A foundation for processing metadata that complements XML and
includes a standard syntax for describing and querying data. Yet to be generally
adopted as of this writing. A component of the proposed Semantic Web. See crosswalk.
re-creation
A digital preservation concept postulating that if the delivery and
content of born digital work such as multimedia or installation art
could be adequately documented in a way that was independent of its native
medium or platform, it would be possible to re-create it using a future medium
or platform.
redundant storage
A digital preservation strategy whereby two or more copies of digital content
are made on the same or different media and stored in different locations under
archival environmental conditions. For example, one set of media may be stored
offsite, or two institutions may agree to store one another's redundant copies.
refreshing
A digital preservation strategy that protects against the possible degradation
of digital content due to storage media decay by copying digital
information held on a particular storage medium to a new medium, of the same
or different type, while keeping the digital information itself in the same format.
refresh rate
The number of times that a screen display is refreshed or repainted per second,
expressed in hertz. The refresh rate for each display depends on the system video
card. Rates of below 70 Hz can cause image flickering and eyestrain,
and, as such, rates of 75 Hz to 85 Hz are recommended.
resampling
May be used interchangeably with resizing. Alternatively, refers to
changing the number and values of pixels in an image, technically by
creating a new, empty bitmap of the desired dimensions and using the
original image pixels as the basis from which to work out the values for each
new pixel using various algorithms. Resampling generally involves interpolation and
should be used cautiously. See compression.
resizing
May be used interchangeably with resampling. Alternatively, it refers
to changing the physical dimensions of an image file without changing its pixel
dimensions (for example, by changing the parameters for default print size).
This would result in the output resolution of an image being set to
a particular value but in no information (no pixels) being gained or lost.
resolution
A relative, rather than an absolute, value, usually expressed as the density
of elements, such as pixels, within a specific distance, most commonly
an inch. See capture resolution, effective resolution, image
resolution, interpolated resolution, monitor resolution, optical
resolution, output resolution, printer resolution, screen
resolution.
resource sharing
The ability to federate collections of digital assets, or simply the metadata describing
those assets, into larger resources where the costs of management are shared.
Or, the ability to use assets and/or metadata outside the system or institution
in which they originated. Examples include the OCLC (Online Computer Library
Center, Inc.) Digital Archive; AMICO (the Art Museum Image Consortium), where
contributors transmit catalog records, digital files, and metadata records
for museum objects to a central repository; RLG (Research Libraries Group)
Cultural Materials; and ARTstor.
RGB (Red, Green, Blue)
An additive color model or system for representing the color spectrum
using combinations of red, green, and blue. Used in video display devices,
and is the standard color system for most digital imaging devices and
applications.
rights management
The description and identification of intellectual property (IP) and
the rights and restrictions relating to it, including the conditions of use.
May become very complicated where dealing with originals and various digital surrogates,
where each instance of a work may have different restrictions placed upon it.
RLG Preservation Metadata Elements
A metadata element set intended to capture the minimum information needed
to manage and maintain digital files over the long term. It captures
technical rather than descriptive information and may be combined with any
descriptive element set to describe an image file.
sample
A digital value derived from measuring a discrete part of an analog original. See sampling.
sample depth
See bit depth, dynamic range.
sampling
The mechanism by which analog signals or objects are digitized.
Sampling involves dividing an analog whole into regularly spaced, smaller discrete
components, measuring the values of each such component, and converting these
measurements to binary code. Provided enough samples are taken, the
readings create the illusion of a continuous (i.e., analog) signal or
object when decoded.
SAN (Storage Area Network)
A sophisticated online storage system where a high-speed special-purpose
subnetwork of shared storage devices is accessible from any server in
the LAN or WAN network of which the SAN is a part. In this system,
data is readily accessible, but because it is stored separately from the server,
server power and network capacity are released for other purposes. See NAS.
scalable
A scalable system is one whose size can be adjusted to meet ongoing requirements
or where each part of a system is flexible enough to accommodate growth or
reduction in another part. Open-source systems are more likely to
be scalable over time, as they allow a greater number of alternative responses
to change.
scanner
A device that captures images from analog sources for computer editing
and display. See digital camera, drum scanner, flatbed
scanner, transparency scanner.
screen resolution
Sometimes used interchangeably with monitor resolution. Otherwise refers
to the number of pixels shown on a computer monitor screen. Screen or
display resolution is variable and may be set to a number of default settings,
such as 800 x 600 or 1024 x 768.
search engine
A set of programs accessed through the use of a Web browser that executes
searches on the Internet. There are various search engines, but most
include a program that goes out and reads searchable Web site pages,
a program that creates an index or catalog of searched pages, and a
program that receives the search request and returns results, usually in the
form of a ranked list chosen from the index. May be confined to searching a
particular site or set of sites.
Semantic Web
An idea or proposal to enhance the "intelligence" of the Web set forth
by its inventor, Tim Berners-Lee. Web content authors would describe, catalogue,
or index sites to improve the ability of future search engines to
recognize context and therefore return more relevant results to Web users. See RDF, XML.
server
A computer program that provides services to other computer programs by responding
to requests and supplying or accepting data. See client/server, storage.
SGML (Standard Generalized Markup Language)
ISO standard ISO/IEC 8879:1986, first
used by the publishing industry, for defining,
specifying, and creating digital documents
that can be delivered, displayed, linked, and
manipulated in a system-independent manner. See DTD, HTML, XML.
SPECTRUM
A broad range of data elements associated with transactions for museum objects
developed by the UK-based mda.
SPIFF (Still Picture Interchange File Format)
A format intended to replace the ubiquitous, as of this writing, JFIF as
the format for images using the JPEG compression algorithm. It offers
additional color spaces as well as expanded functionality.
sRGB
A single, default RGB color space for display devices, codeveloped by
Microsoft and Hewlett-Packard, intended to standardize the many different RGB "flavors." May
be used in conjunction with ICC color profiling.
standards
Formal structures, procedures, and tools designed to promote uniformity and
predictability. Typically developed, adopted, and promoted by large organizations
that can advocate for their broad usage. Data standards enable the exchange
of data, while technology standards enable the delivery of data between systems.
storage
The physical holding of machine-readable data. Data may be stored on
a variety of media, including hard disk, magnetic tape, and optical media such
as CD-ROM. All data and media should be stored under archival environmental
conditions (for instance, with temperature, lighting, and humidity controls)
as a basic digital preservation strategy. See NAS, nearline, offline, online, redundant
storage, SAN, storage networking.
storage networking
Various methods of storing data online while optimizing network performance.
Generally involves the separation of data storage from server processing,
allowing data to be directly transferred between storage devices and client machines
and avoiding server bottlenecks. An Open Storage Network (OSN) is a storage
networking system that emphasizes the use of standards to promote flexibility, interoperability,
and scalability. Storage networking vendors have cooperated to form
the Open Storage Networking Initiative (OSNI), and the term is often used in
marketing. See NAS, SAN.
submaster
See derivative master.
subpixel
Each red, green, and blue element in a pixel is referred to as a subpixel.
Each carries a particular color channel.
TCP (Transmission Control Protocol)
The transport layer in the TCP/IP standard that provides reliable data
delivery over the Internet. It divides files into numbered packets for
sending and reassembles them in the correct order on delivery. It also detects
corrupt or lost packets and resends them.
TCP/IP (Transmission Control Protocol/Internet Protocol)
The ISO standardized suite of network protocols that enables
information systems to link to each other over the Internet, regardless
of their computer platform. TCP and IP are software communication standards used
to allow multiple computers to talk to each other in an error-free fashion.
technology preservation
A digital preservation strategy that involves preserving the complete
technical environment, such as software, drivers, operating systems, fonts,
passwords, and settings, necessary to facilitate access to archived data as
well as its functionality, appearance, and behavior. An alternative approach
is emulation.
TGM-I and TGM-II (Thesaurus for Graphic Materials I and II)
A body of terms maintained by the Library of Congress and used in subject indexing for
pictorial materials such as prints, photographs, drawings, posters, architectural
drawings, cartoons, and pictorial ephemera.
TGN (Getty Thesaurus of Geographic Names)
A controlled vocabulary maintained by the Getty Research Institute that
lists and organizes alternative names for geographic locations.
thesaurus
A structured vocabulary of terms, typically including synonyms and/or hierarchical
relationships, used to organize collections to allow cross-referencing for
purposes of reference or retrieval. See authority, controlled
vocabulary, cataloguing, indexing.
thumbnail
A proxy image, generally scaled to a much smaller size, used to represent a
parent image in circumstances where loading the original is undesirable.
Often used on the Web to display tables of smaller images with links
to a larger view, preserving bandwidth and enabling the display of
more images in the same area for the purposes of browsing.
TIFF (Tagged Image File Format)
A common image file format, TIFF is widely used as a format for storing
uncompressed, or losslessly compressed, digital image data, though
it also supports several compression algorithms. TIFF has gained wide
acceptance for uses such as high-resolution scanning, image archiving, and
editing applications.
transparency scanner
A scanner specifically designed to capture images from film or transparent
media. See drum scanner, digital camera, flatbed scanner.
true-color image
Alternative term for 24-bit images.
ULAN (Union List of Artist Names)
A controlled vocabulary maintained by the Getty Research Institute that
lists and organizes alternative names for artists.
vector graphic
An image composed of mathematically described elements, such as lines, arcs,
and points (vectors), plotted in two- or three-dimensional space. The use
of mathematical formulas to describe an image, instead of pixels,
means vector graphics are not constrained by resolution, allowing
them to be output at any size without loss of detail or other artifacts of
pixel-based processing. Vector-based imaging is inappropriate for continuous
tone imaging. See bitmap.
video card
The circuit board that enables a computer to display information on its screen.
Determines the resolution, number of colors (bit depth), and refresh
rate of display, in combination with the inherent limitations of the
monitor used. Also known as a graphics adapter, display adapter, or video
adapter.
VPN (Virtual Private Network)
A private data network that an organization can use to offer access
to remote users or individuals, which makes use of public telecommunication
infrastructure, such as the Internet, maintaining privacy through the
use of a tunneling protocol and security procedures. Data is encrypted as it
is sent and decrypted as it is received, so the virtual "tunnel" can only be
traversed by properly encrypted data.
VRA Core Categories
A metadata schema specifically designed to describe not only original
works but also their visual surrogates, including digital images, in
considerable detail.
W3C (World Wide Web Consortium)
International consortium that develops vendor-neutral open standards and
specifications for Internet and Web-based transactions, with
the intent of promoting interoperability.
WAN (Wide Area Network)
A network that operates over a geographically dispersed area and is
therefore typically slower than a LAN. WANs often link LANs together
using a high-speed, long-distance connection.
watermark
A unique identifier added to a content file, such as an image, which can be
visible or invisible to viewers. The mark, which could be a statement, symbol,
or hidden encoding, is designed to persist through processing and serve as
evidence of ownership in order to deter piracy.
wavelet compression
Compression technology, which may be lossy
or lossless, that analyzes an image as a whole
rather than dividing it into pixel blocks, as
the JPEG compression algorithm does.
This allows greater compression while still maintaining
acceptable image quality. Wavelet technology
can achieve compression ratios for color images
of 20:1 to 300:1, and of 10:1 to 50:1 for gray
scale images. See JPEG2000.
Web
See World Wide Web.
Web browser
A client program installed on a user's computer that makes requests
of a World Wide Web server using the Hypertext Transfer Protocol (HTTP).
The most common Web browser programs currently in use are Netscape Navigator
and Microsoft Internet Explorer.
Wintel
Personal computers that run one of the Windows operating systems produced by
Microsoft and an Intel microprocessor, such as the Pentium Pro. Also known
as PCs. Generally contrasted with systems that use another operating system,
especially Apple personal computers that use a Macintosh operating system
and Motorola or PowerPC microprocessors.
World Wide Web
A vast, distributed client/server architecture for retrieving hypermedia
or hypertext (interactive documents and media joined together by "links" or
selectable connections) over the Internet using the Hypertext Transfer
Protocol (HTTP).
wrapper
A file used to encapsulate another file or collection of files. For example,
the METS system either "contains" a digital file and its metadata
in an XML file that describes them or points to files stored elsewhere.
XHTML (eXtensible HyperText Markup Language)
A reformulation of HTML as an application of XML designed to
express Web pages. Users can extend XHTML to include new elements and
attributes, and XHTML documents can be read and validated with standard XML
tools.
XML (eXtensible Markup Language)
A simplified subset of SGML designed for use with the World Wide
Web that provides for more sophisticated, meaningful (semantic), and flexible
data structuring and validation than HTML. XML is widely forecast to
be the successor to HTML as the language of the Web and is an essential
component of the proposed Semantic Web. See XHTML, XSD, XSL,
XSLT.
XML-enabled
Designed to be compatible with XML. For instance, XML-enabled databases use middleware to
translate between XML documents and traditional relational or object-relational databases. See native-XML.
XSD (XML Schema Definition)
A specification designed to express relational or non-narrative data in XML.
Provides a standard way to validate data sets and to exchange them between
applications. See database, DTD.
XSL (eXtensible Stylesheet Language)
The language used to create style sheets that describe how XML-structured
data is to be displayed to Web users.
XSLT (eXtensible Stylesheet Language Transformations)
May be regarded as an extension of XSL. Provides a standard way to reorganize
the data represented in one XML document into a new XML document with
a different structure, or into another format altogether.
Z39.50
ISO 23950 and ANSI/NISO Z39.50
standard information retrieval protocol, a client/server-based
method of searching and retrieving information
from heterogeneous (usually remote) databases,
most often used in bibliographic implementations.
The ZNG (Z39.50 Next Generation) Initiative aims
to update Z39.50 and make it compatible with XML and
other current Web technologies.
The following sources were referred to in creating this glossary:
Andy Moore's The Imaging Glossary, Electronic Document and Image
Processing Terms, Acronyms and Concepts (1991); The Electronic
Imaging Glossary (1994), compiled by Mimi King for the Library
and Information Technology Association of the American Library Association;
Internet.com's Webopedia; the FOLDOC Free On-Line Dictionary of Computing;
and TechTarget's IT-specific encyclopedia Whatis?com. Maria Bonn,
Nigel Kerr, and Jim Schlemmer contributed to the development of further
definitions used in the first edition.
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