This document is a glossary of terms used in other documents produced by
the Device Independence Working Group (DIWG). Details of the entire series of
documents can be found on the W3C Device
Independence Activity home page.
This section describes the status of this document at the time of its
publication. Other documents may supersede this document. A list of current
W3C publications and the latest revision of this technical report can be
found in the W3C technical reports index
at http://www.w3.org/TR/.
The glossary is maintained as a Working Draft of a future W3C Note. This
allows it to be revised at appropriate intervals. Updates take place in
support of new work being carried out by the DIWG. In general, it is
inappropriate to use W3C Working Drafts as formal reference material or to
cite them as other than "work in progress". Because this document is subject
to change, other authors wishing to cite definitions in this glossary should
exercise caution. Updates to the glossary are made in such a way as to avoid
invalidating references, as long as those references conform to the
mechanisms described in the section Using and Maintaining the Glossary.
However, in support of its work, DIWG may need to modify definitions in newer
versions of this document.
A list of current public W3C Working Drafts can be found at http://www.w3.org/TR.
Publication as a Working Draft does not imply endorsement by the W3C
Membership. This is a draft document and may be updated, replaced or
obsoleted by other documents at any time. It is inappropriate to cite this
document as other than work in progress.
Comments on this document can be sent to www-di@w3.org, the public forum for
discussion of the W3C's work on Device Independence. To subscribe, send an
email to www-di-request@w3.org
with the word subscribe in the subject line (include the word unsubscribe if
you want to unsubscribe). The archive for the list
is accessible online.
A combination of hardware (including one or more devices and network connections) and software
(including one or more user agents) that
allows a user to perceive and interact with the Web using one or more modalities. (sight, sound, keyboard, voice
etc.)
a process of selection, generation or modification that produces one
or more perceivable units in
response to a requested uniform resource identifier
in a given delivery context.
A set of factors, specified by a user or
other aspects of the delivery
context, that may affect the functionality of an application,
independently of its adaptation and
delivery, and so change the resultant user experience."
Some set of material created as a single entity by an author.
Examples include a collection of markup, a style sheet, and a media resource, such as an image or audio clip.
The mechanism for selecting the appropriate HTTP representation when servicing
a request. The HTTP representation of entities in
any response can be negotiated (including error responses).
A set of attributes that characterizes the capabilities of
the access mechanism, the
preferences of the user and other aspects of
the context into which a web page is to be delivered.
A set of material transferred between two cooperating web programs as
the response to a single HTTP request.
The transfer might, for example, be between an origen server and a user agent.
Users are not normally aware of individual delivery units.
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 do not know that it is an intermediary.
An HTTP server which acts as an
intermediary for some other HTTP server.
Unlike an HTTP proxy, an HTTP gateway
receives requests as if it were the origen
server for the requested resource; the
requesting HTTP client may not be aware
that it is communicating with an HTTP gateway.
An intermediary program which acts as both an HTTP server and as an HTTP client for the purpose of making
requests on behalf of other HTTP
clients.
HTTP requests are serviced internally
or by passing them on, with possible translation, to other HTTP servers. An HTTP proxy must implement
both the client and server requirements of this specification. A
"transparent proxy" is a proxy that does not modify the HTTP request or the HTTP response beyond what is required for
proxy authentication and identification. A "non-transparent proxy" is a
proxy that modifies the HTTP request or
HTTP response in order to provide some
added service to the user agent, such as
group annotation services, media type transformation, protocol
reduction, or anonymity filtering. Except where either transparent or
non-transparent behavior is explicitly stated, the HTTP proxy
requirements apply to both types of proxies.
An HTTP message sent by an HTTP client
requesting that some operation be performed on some resource. Also, the act of sending such a
message is termed making a request.
An application program that accepts connections in order to service
HTTP requests by sending back HTTP responses.
Any given program may be capable of being both an HTTP client and an HTTP server; our use of
these terms refers only to the role being performed by the program for
a particular connection, rather than to the program's capabilities in
general. Likewise, any HTTP server may
act as an origen server, HTTP proxy, HTTP
gateway, or tunnel, switching behavior based on the nature of each
request.
An activity by which a user can influence the data and processing of
an application by modifying the information associated with an active perceivable unit.
A common form of this kind of activity is the entry of data into an
active perceivable unit that
contains a form.
The type of communication channel used for interaction . This might be, for example,
visual, gestural or based on speech. It also covers the way an idea is
expressed or perceived, or the manner in which an action is performed.
This definition is based on unpublished work of the Multimodal
Interaction group.
Multiple authoring represents one end of a spectrum of
authoring styles that include single
authoring and flexible
authoring. It represents a theoretical extreme that is rarely
achieved in practice. Though it offers authors complete control over
the user experience on each device, the associated development and
maintenance costs are usually considered prohibitive.
User agents may choose to render some
or all of the material they receive in a delivery unit as a single perceivable
unit or as multiple perceivable units.
Most perceivable units provide both presentation and the means for interaction. However, on some types of
device, such as printers, perceivable units might contain only
presentation.
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.
A set of preferences, specified by a user,
that may affect the way the user agent renders a perceivable unit, and
so change the resultant user experience.
A network data object or service that can be
identified by a URI.
Resources may be available in multiple representations (e.g. multiple
languages, data formats, size, resolutions) or vary in other ways.
One specific rendition of a resource at a specific point in time and
space.
A conceptual mapping exists between a resource and a resource manifestation (or set
of manifestations), in the sense that the resource has certain
properties - e.g., its URI, its intended purpose,
etc. - which are inherited by each manifestation, although the specific
structure, form, and content of the manifestation may vary according to
factors such as the environment in which it is displayed, the time it
is accessed, etc. Regardless of the form the manifestation's rendering
ultimately takes, the conceptual mapping to the resource is preserved.
Single authoring represents one end of a spectrum of
authoring styles that include multiple authoring and flexible authoring. It represents a
theoretical extreme that is rarely achieved in practice. Though,
theoretically, it offers the minimum development cost, limitations in
practical adaptation systems mean that compromises are necessary in the
final user experiences. These compromises are often considered
unacceptable.
A resource may have one, or more than
one, representation(s) associated with it at any given instant. Each of
these representations is termed a `variant.' Use of the term `variant'
does not necessarily imply that the resource is subject to content negotiation.
A collection of information, consisting of one or more resources, intended to be rendered
simultaneously, and identified by a single Uniform Resource
Identifier.
More specifically, a web page consists of a resource with zero, one, or more embedded resources intended to be rendered as a single
unit, and referred to by the URI of the one resource which is not embedded.
This section documents the way in which the glossary should be used from
other DIWG documents. It also documents how changes are to be made to the
glossary itself in a way that will not invalidate links to the
definitions.
Every definition in the glossary has an associated anchor. As a
consequence every definition can be directly referenced externally from other
documents. Such references should use the public URL associated with the DIWG
glossary. For the latest version of the glossary, this has been established
as
To refer to a particular definition, a document should create a URL based
on the appropriately dated, public URL and the fragment identifier for the
definition. Fragment identifiers consist of the definition name, in
lowercase, with words separated by dashes and prefixed by
def. For example, the fragment identifier for the definition
of User Agent is def-user-agent, and for
Navigation is def-navigation. The URL to
use for the definition of Navigation for the dated version mentioned above
would be:
One important guarantee for documents that reference the glossary is that
the fragment identifier for a given definition never changes. If, for
example, a new version of a particular definition is needed, the older
version will be retained within the glossary with its fragment identifier.
The new version will be given a new identifier. The process used to maintain
the glossary and to retain this uniqueness of definition identifiers is
described in the following section.
In addition to referring directly to individual definitions in the
glossary, documents that use it should include a reference to the dated
version in use in their References section. The following is an example of
such a reference:
Glossary of
Terms for Device Independence (version used for definitions)
The DIWG glossary will remain a public working draft. This reflects the
need to update it as new work is carried out in DIWG. The need to revise the
glossary, and in particular the potential requirement to revise definitions,
leads to a need for a mechanism that can allow older documents to refer
unambiguously to older revisions of particular definitions.
Once a version of the glossary has been published, the definitions it
contains have fragment identifiers that must not be changed. As new
definitions are added they are given new identifiers. This poses no issues
for documents authored before the new definitions were published. However,
when a definition is revised, it is vital that older documents that used the
old version are still valid. They are protected by the use of version
identification within the fragment identifiers. In addition, the old versions
of definitions are maintained in Appendix
B of the glossary.
To revise a glossary definition, the following steps must be carried
out:
The existing definition, complete with fragment identifier, must be
copied to Appendix B.
The definition must be updated within the main part of the
glossary.
The revised definition must be given an updated fragment identifier
constructed by adding a version number where none exists, or incrementing
it if one already exists. For example, if the fragment identifier before
revision were #def-navigation it would become #def-navigation-v2. Alternatively, if
the fragment identifier before revision were
#def-navigation-v7 it would become
#def-navigation-v8.
All references to the definition within the glossary
itself must be updated to refer to this new fragment identifier. In
addition, all definitions that refer to the revised definition must be
reviewed to see whether they need modification because of the change. If
so, this same procedure must be applied those definitions and new
versions must be created.
The old definition that has been moved to Appendix B must have a reference added
that refers to the newer definition in the body of the glossary. As an
example, the reference for an old version of the definition of Navigation
might include the reference:
"This definition has been superseded. There is a newer definition of Navigation".
Notice that these links should not be updated
when a new version of a definition is added. By not changing them, they
form a chain through the versions of the definition from the one
referenced by the external document up to the latest version.
This section contains definitions that have been superseded within the
existing glossary. The first section holds definitions that have been
updated. The second section holds definitions that have been removed.
A set of attributes that characterizes the capabilities of
the access mechanism, and the
preferences of the user. This definition has
been superseded. There is a new definition of Delivery Context.
The act of dividing up one or more authored units during creation of a set
of perceivable units appropriate
for a particular delivery context. This definition has been superseded.
There is a new definition of decomposition.
The act of dividing up one or more authored units to create a set of perceivable units appropriate for a
particular delivery context. This term has been replaced by the new
term decomposition
Members of the W3C Device Independence Working Group have helped develop
this Working Draft through their comments, proposals and discussions at
teleconferences, face-to-face meetings and via the group discussion list.
At the time of publication, the principal and active members of the group
were as follows: