Extensible 3D (X3D)
Part 1: Architecture and base components

3 Definitions, acronyms, and abbreviated terms

# 3.1 Definitions

For the purposes of this document , the following definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

- ISO Online browsing platform: available at www.iso.org/obp
- IEC Electropedia: available at www.electropedia.org

## 3.1.1
activate

cause a sensor node to generate an isActive event

## 3.1.2
ancestor

node which is an antecedent of another node in the transformation hierarchy

## 3.1.3
audio graph

structured collection of nodes that process audio inputs and outputs

## 3.1.4
author

person or agent that creates X3D files

## 3.1.5
authoring tool

See generator.

## 3.1.6
avatar

abstract representation of the user in an X3D world

## 3.1.7
bearing

straight line passing through the pointer location in the direction of the pointer

## 3.1.8
bindable node

node that may have many instances in a scene graph but only one instance may be active at any instant of time

## 3.1.9
browser

computer program that interprets X3D files, presents their content to a user on a display device, and allows the user to interact with worlds defined by X3D files by means of a user interface

## 3.1.10
browser extension

nodes defined using the prototyping mechanism that are understood only by certain browsers

## 3.1.11
built-in node

node of a type explicitly defined in this document

## 3.1.12
callback

function defined in a scripting language to which events are passed

## 3.1.13
child

instance of a children node

## 3.1.14
children node

one of a set of node types, instances of which can be collected in a group to share specific properties dependent on the type of the grouping node

## 3.1.15
client system

computer system, attached to a network, that relies on another computer (the server) for essential processing functions

## 3.1.16
collision proxy

node used as a substitute for all of a Collision node's children during collision detection

## 3.1.17
colour model

characterization of a colour space in terms of explicit parameters

## 3.1.18
culling

process of identifying objects or parts of objects which do not need to be processed further by the browser in order to produce the desired view of a world

## 3.1.19
descendant

node which descends from another node in the transformation hierarchy (a children node)

## 3.1.20
display device

graphics device on which X3D worlds may be rendered

## 3.1.21
drag sensor

pointing device sensor that causes events to be generated in response to sensor-dependent pointer motions

## 3.1.22
environmental sensor

sensor node that generates events based on the location of the viewpoint in the world or in relation to objects in the world

## 3.1.23
event

message sent from one node to another as defined by a ROUTE

## 3.1.24
event cascade

sequence of events initiated by a script or sensor event and propagated from node to node along one or more routes all of which are considered to have occurred simultaneously

(see Concepts, 4.4.8.3 Execution model)

## 3.1.25
execution model

rules governing how events are processed by browsers and scripts

## 3.1.26
external prototype

prototype defined in an external file and referenced by a URL

## 3.1.27
field

property or attribute of a node

## 3.1.28
field name

identifier of a field

## 3.1.29
frame

single rendering of a world on a display device or a single time-step in a simulation

## 3.1.30
generator

computer program which creates X3D files

## 3.1.31
geometric property node

node defining the properties of a specific geometry node

## 3.1.32
geometry node

node containing mathematical descriptions of points, lines, surfaces, text strings and solids

## 3.1.33
grab

receive events from activated pointing devices

## 3.1.34
grouping node

one of a set of node types which include a list of nodes, referred to as its children nodes

## 3.1.35
host application

client application with which the browser communicates using the SAI

## 3.1.36
image

two-dimensional (2D) rectangular array of pixel values

## 3.1.37
immersive

creating the illusion of being inside a computer-generated scene

## 3.1.38
in-lining

mechanism by which one X3D file is hierarchically included in another

## 3.1.39
instance

the node created by an instantiation

## 3.1.40
instantiation

the creation of a node based on its node type

## 3.1.41
interpolator node

node that defines a piece-wise or smoothly continuous interpolation

## 3.1.42
intranet

private network that uses the same protocols and standards as the Internet

## 3.1.43
level of detail

amount of detail or complexity which is displayed at any particular time for any particular object

## 3.1.44
line terminator

linefeed character (0x0A) and/or carriage return character (0x0D)

## 3.1.45
loop

sequence of events which would result in a specific event generator sending more than one event with the same timestamp

## 3.1.46
multimedia

integrated presentation, typically on a computer, of content of various types, such as computer graphics, audio, and video

## 3.1.47
network

set of interconnected computers

## 3.1.48
node

fundamental component of a scene graph that defines model information, such as graph structure, geometry, animation, interaction, object metadata, rendering, or display

## 3.1.49
node type

characteristic of each node that describes, in general, its particular semantics

## 3.1.50
object

collection of data and procedures, packaged according to the rules and syntax defined in this document

NOTE This term is usually synonymous with node.

## 3.1.51
order of preference

order (specified by the user) in which a list of field values is processed by the browser

## 3.1.52
panorama

background texture that is placed behind all geometry in the scene and in front of the ground and sky

## 3.1.53
parent

node which is an instance of a grouping node

## 3.1.54
pixel

one element of an image specified as a matrix of colour elements

## 3.1.55
pointer

location and direction in the virtual world defined by the pointing device with which the user is currently interacting with the virtual world

## 3.1.56
pointing device

hardware device connected to the user's computer by which the user directly controls the location and direction of the pointer

## 3.1.57
pointing device sensor

sensor node that generates events based on user actions, such as pointing device motions or button activations

## 3.1.58
polyline

piecewise linear curve

## 3.1.59
profile

named collection of criteria for functionality and conformance that defines an implementable subset of a standard

## 3.1.60
prototype

definition of a new node type in terms of the nodes defined in this document

## 3.1.61
prototyping

mechanism for extending the set of node types from within a X3D file

## 3.1.62
ROUTE

connection between a node generating an event and a node receiving the event

## 3.1.63
scene graph

ordered set of nodes and statements

## 3.1.64
script

set of procedural functions normally executed as part of an event cascade

## 3.1.65
scripting

process of creating or referring to a script

## 3.1.66
scripting language

system of syntactical and semantic constructs used to define and automate procedures and processes on a computer

## 3.1.67
sensor node

node that enables the user to interact with the world in the scene graph hierarchy

## 3.1.68
separator character

UTF-8 character used to separate syntactical entities in an X3D file

## 3.1.69
sibling

node which shares a parent with other nodes

## 3.1.70
simulation tick

smallest time unit capable of being identified in a digital simulation of analog time

## 3.1.71
slerp

spherical linear interpolation for animating 3D rotation values

## 3.1.72
special group node

grouping node that exhibits special behaviour ( e.g., Switch or LOD)

## 3.1.73
statement

A statement specifies fundamental scene-related information

## 3.1.74
texel

pixel in an image used as a texture

## 3.1.75
texture

image used to create visual appearance effects when applied to geometry nodes

## 3.1.76
texture coordinates

set of coordinates used to map a texture to geometry

## 3.1.77
time

monotonically increasing value generated by a node

## 3.1.78
timestamp

that part of an event that describes the time the event occurred and that caused the message to be sent

## 3.1.79
transformation hierarchy

subset of the scene graph consisting of nodes that have well-defined coordinate systems

## 3.1.80
transparency chunk

section of a PNG file containing transparency information (derived from ISO/IEC 15948)

## 3.1.81
traverse

process the nodes in a scene graph in the correct order

## 3.1.82
user

person or agent who uses and interacts with X3D files by means of a browser

## 3.1.83
viewer

location, direction, and viewing angle in a virtual world that determines the portion of the virtual world presented by the browser to the user

## 3.1.84
virtual world

See world.

## 3.1.85
white space

one or more consecutive occurrences of a separator character

## 3.1.86
world

collection of one or more X3D files (potentially including other multimedia content) that is interpreted by an X3D browser to present an interactive experience to the user that is consistent with the intent of the author

## 3.1.87
world coordinate space

coordinate system in which each X3D world is defined

## 3.1.88
X3D browser

See browser.

## 3.1.89
X3D document server

computer program that locates and transmits X3D files and supporting files in response to requests from browsers

## 3.1.90
X3D file

set of X3D nodes and statements as defined in this document

## 3.1.91
XY plane

plane perpendicular to the Z-axis that passes through the point Z = 0.0

## 3.1.92
YZ plane

plane perpendicular to the X-axis that passes through the point X = 0.0

## 3.1.93
ZX plane

plane perpendicular to the Y-axis that passes through the point Y = 0.0

# 3.2 Acronyms and abbreviated terms

For the purposes of this document, the following expansion of acronyms and abbreviated terms apply:

## 3.2.1
CAD

Computer-Assisted Design

## 3.2.2
HSV

Hue, Saturation, and Value colour model

[FOLEY]

## 3.2.3
JPEG

Joint Photographic Experts Group

[ISO/IEC 10918-1]

## 3.2.4
MIDI

Musical Instrument Digital Interface. A standard for digital music representation

[MIDI]

## 3.2.5
MIME

Multipurpose Internet Mail Extension

[IETF RFC2077]

## 3.2.6
MF

Multiple-valued field

(see Field type reference, 5.2.2 X3DArrayField)

## 3.2.7
MPEG

Moving Picture Experts Group

[ISO/IEC 11172-1]

## 3.2.8
PNG

Portable Network Graphics. A specification for representing two-dimensional images in files

[ISO/IEC 15948]

## 3.2.9
RGB

Red, Green, and Blue colour model

[FOLEY]

## 3.2.10
RURL

Relative Uniform Resource Locator

[URI]

## 3.2.11
SAI

Scene Access Interface

## 3.2.12
SF

Single-valued field

(see Field type reference, 5.2.3 X3DField)

## 3.2.13
UCS

Universal multiple-octet coded Character Set

[ISO/IEC 10646]

## 3.2.14
URI

Universal Resource Identifier

[URI]

## 3.2.15
URL

Uniform Resource Locator

[URI] [RFC8089]

## 3.2.16
URN

Universal Resource Name

[RFC8141]

## 3.2.17
UTF-8

variable-length 8-bit Universal multiple-octet coded character set Transformation Format

[ISO/IEC 10646]