Information technology -- Computer graphics and image processing -- The Virtual Reality Modeling Language

Technologies de l'information -- Infographie et traitement de l'image -- Le langage de modélisation de la réalité virtuelle

General Information

Publication Date
Current Stage
9020 - International Standard under periodical review
Start Date
Ref Project

Buy Standard

ISO/IEC 14772-1:1997 - Information technology -- Computer graphics and image processing -- The Virtual Reality Modeling Language
English language
236 pages
sale 15% off
sale 15% off

Standards Content (sample)

First edition
Information technology - Computer
graphics and image processing - The
Virtual Reality Modeling Language -
Part 1:
Functional specification and UTF-8 encoding
Technologies de I’informa tion -
Infographie et traitement de l’image - Le
langage de mod6lisation de rGalit6 virtuelle -
Partie 1: Spkification fonctionnelle et codage UTF-8
Reference number
ISO/1 EC 14772-1: 1997(E)
---------------------- Page: 1 ----------------------
ISO/lEC 14772-1: 1997( E)

ISO (the International Organization for Standardization) and IEC (the International

Electrotechnical Commission) form a specialized System for worldwide standardization.

National bodies that are members of ISO or IEC participate in the development of

International Standards through technical comm ittees established by the respective

organization to deal with particular Gelds sf technical activity. ISO and IEC technical

committees collaborate in Felds of mutual interest. Other international organizations,

govemmental and non-governmental, in liaison with ISO and IEC, also take part in the

See for information on ISO and
http: //www. i e c . c h for information on IEC.

In the Geld of information technology, ISO and IEC have established a joint technical

committee, ISO/IEC JTC P. Draft International Standards adopted by the joint technical

committee are circulated to national bodies for voting. Publication as an International

Standard requires approval by at least 75% of the national bodies casting a vote. See forinformationonJTC1.
International Standard ISO/IEC 14772 was prepared by Joint Technical Committee
ISO/IEC JTC 1, In$Srmation technoloa1, Subcommittee 24, Computer graphics and
image processing, in collaboration with The VRML Consortium, Inc.
(ht-tp : / /www . vrml . arg) and the VRML moderated email list (www-

ISO/IEC 14 ’772 consists of the following gart, under the general title lnformation

technology -- Computer graphics and image processing -- The Virtual Reality Modeling

Part 1: Functionab specljkation and LTF-8 encoding.
Further Parts will follow.

Annexes A to C form an integral part sf this gart of ISO/IEC 14772. Annexes D to F are

for information only.

This part of ISO/IEC 14472 is distributed as both a hard copy edition and an HTME file

which is on the attached CD-ROM. The Paper and the electronie Versions contain the

same material. However, the structure and presentation are more relevant to the document

as viewed On-Screen. Please note that the electronie file must be viewed using a recent

version of a web browser.
0 ISO/IEC 1997

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or

utilized in any form or by any means, electronie or mechanical, including photocopying and micro-

film, without permission in writing from the publisher.
ISO/IEC Copyright Office l Case postale 56 l CH-121 1 Geneve 20 l Switzerland
Printed in Switzerland
---------------------- Page: 2 ----------------------
ISO/IEC 14772=1:1997(E)
4, “dafqgf#Jiv
*P urpose
The Virtual Reality Modeling Language (VRML) is a file format for describing
interactive 3D objects and worlds. VRML is designed to be used on the Internet,

intranets, and local client Systems. VRML is also intended to be a universal interchange

format for integrated 3D graphics and multimedia. VRML may be used in a variety of

application areas such as engineering and scientific visualization, multimedia

presentations, entertainment and educational titles, web pages, and shared virtual worlds.

gD esign Criteria
VRML has been designed to fulfill the following requirements:
Enable the development of Computer programs capable of creating, editing, and
maintaining VRML files, as well as automatic translation programs for converting
other commonly used 3D file formats into VRML files.
Provide the ability to use and combine dynamic 3D objects within a VRML world
and thus allow re-usability.
Provide the ability to add new Object types not explicitly defined in VRML.
Be capable of implementation
Capable of implementation on a wide range of Systems.
Emphasize scalable, interactive Performance on a wide variety of computing
Enable arbitrarily large dynamic 3D worlds.
* Characteristics of VRML
VRML is capable of representing static and animated dynamic 3D and multimedia

objects with hyperlinks to other media such as text, Sounds, movies, and images. VRML

browsers, as well as authoring tools for the creation of VRML files, are widely available

for many different platforms.

VRML supports an extensibility model that allows new dynamic 3D objects to be defined

. . .
---------------------- Page: 3 ----------------------
ISO/IEC 14772-1:1997(E)
allowing application communities to develop interoperable extensions to the base
Standard. There are mappings between VRML objects and commonly used 3D
application programmer interface (API) features.
---------------------- Page: 4 ----------------------
Information technology --
Computer graphics and image processing --
The Virtual Reality Modeling Language --
Part 1: Functional specification and UTF-8 encoding
1 Scope

ISO/IEC 14772, the Virtual Reality Modeling Language (VRML), defines a file format that integrates 3D graphics

and multimedia. Conceptually, each VRML file is a 3D time-based space that contains graphic and aural objects that

tan be dynamically modified through a variety of mechanisms. This part of ISO/IEC 14772 defines a primary set of

objects and mechanisms that encourage composition, encapsulation, and extension.

The semantics of VRML describe an abstract functional behaviour of time-based, interactive 3D, multimedia

information. ISO/IEC 14772 does not Befine physical devices or any other implementation-dependent concepts (e.g.,

Screen resolution and input devices). ISO/IEC 14772 is intended for a wide variety of devices and applications, and

provides wide latitude in interpretation and implementation of the functionality. For example, ISO/IEC 14772 does

not assume the existente of a mouse or 2D display device.
Esch VRML file:

a. implicitly establishes a world coordinate space for all objects defmed in the file, as well as all objects

included by the file;
b. explicitly defines and composes a set of 3D and multimedia objects;
C. tan specify hyperlinks to other files and applications;
d. tan define Object behaviours.

An important characteristic of VRML files is the ability to compose files together through inclusion and to relate

files together through hyperlinking. For example, consider the file earth.wrZ which specifies a world that contains a

sphere representing the earth. This file may also contain references to a variety of other VRML files representing

cities on the earth (e.g., file Paris. wrl). The enclosing file, earth. wrl, defines the coordinate System that all the cities

reside in. Esch City file defines the world coordinate System that the city resides in but that becomes a local

coordinate System when contained by the earth file.

Hierarchical file inclusion enables the creation of arbitrarily large, dynamic worlds. Therefore, VRML ensures that

each file is completely described by the objects contained within it.

Another essential characteristic of VRML is that it is intended to be used in a distributed environment such as the

World Wide Web. There are various objects and mechanisms built into the language that support multiple

---------------------- Page: 5 ----------------------
ISO/IEC 14772-1:1997(E) 0 ISOAEC
distributed files, including:
e. in-lining of other VRML files;
f. hyperlinking to other files;
using established Internet and ISO Standards for other file formats;
h. defining a compact Syntax.
---------------------- Page: 6 ----------------------
0 ISO/IEC ISO/IEC 14772-1: 1997(E)
2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions

of this part of ISO/IEC 14772. For dated references, subsequent amendments to, or revisions of, any sf these

publications do not apply. However, Parties to agreements based on this part of ISO/IEC 14772 are encouraged to

investigate the possibility of applying the most recent editions of the normative documents indicated below. For

undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC

maintain registers of currently valid International Standards.
Annex E, Bibliography, contains a list of informative documents and technology.
Identifier Reference

IETF RFC 1766, Tags for the Identification of Languages, Internet Standards track protocol.

http:, 1766.txt

ISO/IEC 8632: 1992 (all Parts) Information technology -- Computer graphics -- Metafile for the

CGM storage and transfer of picture description information. WORDS=8632

ISO/IEC DIS 16262 Information technology -- ECMAScript: A general purpose, Cross-platform

programming language.
http:/! WORDS=l6262
HTML 3.2 Reference Specification.
ISO 639: 1988 Code for the representation of names of languages., 639.html
ISO 3 166: 1997 (all Parts) Codes for the representation of names of countries
and their subdivisions.

ISO/IEC 8859-1: 1987 Information technology -- 8-bit Single-byte coded graphic Character sets --

Part 1: Latin alphabet No. 1. WORDS=8859
---------------------- Page: 7 ----------------------
ISO/IEC 1477201:1997(E) 0 ISO/IEC
ISO/IEC 9899: 1990 Programming languages -- C.

ISO/IEC 1064 1: 1993 Information technology -- Computer graphics and image processing --

ISOG Conformance testing of implernentations of graphics Standards. 1064 1 &searchtype=refnumber

“The Java Language Specification” by James Gosling, Bill Joy and Guy Steele, Addison

Wesley, Reading Massachusetts, 1996, ISBN 0-20 1-6345 1- 1.

“The Java Virtual Machine Specification” by Tim Lindhold and Frank Yellin, Addison Wesley,

Reading Massachusetts, 1996, ISBN 0-20 l -63452-X.
“JPEG File Interchange Format,” JFIF, Version 1.02, 1992.

ISO/IEC 109 18- 1: 1994 Information technology -- Digital compression and coding of

continuous-tone still images: Requirements and guidelines. WORDS= 109 18&searchtype=refnumber

Complete MIDI 1 .O Detailed Specification, MIDI Manufacturers Association,
MIDI P.O. Box 3 173, La Habra, CA 90632 USA 1996.

ISO/IEC 11172- 1: 1993 Information technology -- Coding of moving pictures and associated

MPEG audio for digital storage media at up to about 1,5 Mbit/s -- Part 1: Systems. 11172

PNG (Portable Network Graphits), Specification Version 1 .O, W3C Recommendation, 1

PNG October 1996.
q .

IETF RFC 1808 Relative Uniform Resource Locator, Internet Standards track protocol.

RURL 1808.txt
IETF RFC 1738 Uniform Resource Locator, Internet Standards track protocol.
---------------------- Page: 8 ----------------------
ISO/IEC 14772-1: 1997(E)

ISO/IEC 10646-1: 1993 Information technology -- Universal Multiple-Octet Coded Character

Set (UCS) - Part 1: Architecture and Basic Multilingual Plane, Internet Standards track protocol.

UTF8 WORDS=10646,

---------------------- Page: 9 ----------------------
ISO/IEC 14772-1: 1997(E)
3 Defhitions
For the purposes of this part of ISO/IEC 14722, the following definitions apply.
3.1 activate

To Cause a Sensor node to generate an “isActive” event. The various types of Sensor nodes are “activated” by user

interactions, the passage of time, or other events. Only active Sensor nodes affect the user ’s experience. A Script

node is activated when it receives an event. A pointing device such as a mouse is activated when one of its buttons is

depressed by a User. See 4.12.2, Script execution, for details.
3.2 ancestor
A node which is an antecedent of another node in the transformation hierarchy.
3.3 author

A person or agent that creates VML fZes. Authors typically use generators to assist them.

3.4 authoring tool
See generator.
3.5 avatar

The abstract representation of the user in a VRML world. The physical dimensions of the avatar are used for

collision detection and terrain following. See 6.29, NavigationInfo, for details.

3.6 bearing

A straight line passing through the pointer location in the direction of the pointer. If multiple Sensors’ geometry

intersect this line, only the Sensor nearest the viewer will be eligible to generate events regardless of material and

texture properties (e.g., transparency).
3.7 bindable node

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

node of type Background, Fog, NavigationInfo, or Viewpoint. See 4.6.10, Bindable children nodes, for details.

3.8 browser

A Computer program that interprets VML files, presents their content to a user on a display device, and allows the

user to interact with worlds defined by VRML files by means of a user interface.
---------------------- Page: 10 ----------------------
ISO/IEC 14772-1: 1997(E)
3.9 browser extension

Nodes defined using the prototyping mechanism that are understood only by certain browsers. See

4.93, Browser extensions, for details.
3.10 built-in node
A node of a olpe explicitly defmed in this part of ISO/IEC 14772.
3.11 callback

A function defined in a scripting language to which events are passed. See 4.123, EventIn handling, for details.

3.12 candidate

One of potentially several choices. The user or the browser will select none or one of the choices when all

candidates are identified. See 46.10, Bindable children nodes, and 6.2, Anchor, for details.

3.13 Child
An instance of a children node.
3.14 children node

One of a set of node types, instances of which tan be collected in a group to share specific properties dependent on

the type of the Cqroupin,g node. See 4.6.5, Grouping and children nodes, for a list of allowable children nodes.

3.15 client System
network, that relies on another Computer (the server) for essential processing
A Computer System, attached to a
functions. Many client Systems also function as stand-alone Computers.
3.16 collision proxy

A node used as a Substitute for all of a Collision node ’s children during collision detection. See 6.8, Collision, for

3.17 colour model

Characterization of a colour space in terms of explicit Parameters. ISO/IEC 14772 allows colours to be defined only

with the RGB colour model. However, colour interpolation is performed in the HSV colour space.

3.18 culling

The process of identifying ohiects 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.
---------------------- Page: 11 ----------------------
ISOLIEC 14772=1:1997(E)
3.19 descendant

A node which descends from another node in the transförmation hierarchy. A children node.

3.20 display device
A graphics device on which VRML worlds may be rendered.
3.21 drag Sensor

A pointin& device Sensor that Causes events to be generated in response to sensor-dependent pointer motions. For

example, the SphereSensor generates spherical rotation events. A node of type CylinderSensor, PlaneSensor, or

SphereSensor. See 4.6.7, Sensor nodes, and, Drag Sensors, for details.
3.22 environmental Sensor

A Sensor node that generates events based on the location of the viewpoint in the world or in relation to obiects in

the world. The TimeSensor node generates events at regular intervals in time. A node of type Collision,

ProximitySensor, TimeSensor, or VisibilitySensor. See, Environmental Sensors, for details.

3.23 event

A messa,ce sent from one node to another as defined by a reute. Events Signal extemal Stimuli, changes to field

v - .

values, and interactions between nodes. An event consists of a timestamp and a field value.

3.24 event cascade

A sequence of events initiated by a script or Sensor event and propagated from node to node along one or more

routes. All events in an event cascade are considered to have occurred simultaneously. See 4.103, Execution model,

for details.
3.25 eventIn
A logical receptor attached to a node which receives events.
3.26 eventout

A logical output terminal attached to a node from which events are sent. The eventout also stores the event most

recently sent.
3.27 execution model
The rules goveming how events are processed by browsers and scripts.
3.28 exposed field

A field that is capable of receiving events via an eventln to Change its value(s), and generating events via an

---------------------- Page: 12 ----------------------
ISO/IEC 14772-1: 1997(E)
eventout when its value(s) Change.
3.29 external prototype
A prototype defmed in an extemal file and referenced by a URL.
3.30 field

A property or attribute of a node. Esch node type has a fixed set of Felds. Fields may contain various kinds of data

and one or many values. Esch field has a default value.
3.31 field name
The identifier of aJ;eZd. Field names are unique within the scope of the node.
3.32 file

A collection of related data. A file may be stored on physical media or may exist as a data stream or as data within a

Computer program.
3.33 frame

A Single rendering of a wor/d on a display device or a Single time-step in a Simulation.

3.34 generator

A Computer program which creates VRML files. A generator may be used by a person or operate automatically.

Synonymous with authoring tool.
3.35 geometric property node

A node defining the properties of a specific geometry node. A node of type Color, Coordinate, Normal, or

Texturecoordinate. See, Geometrie property nodes, for details.
3.36 geometric Sensor node

A node that generates events based on user actions, such as a mouse click or navigating close to a particular Object.

A node of type CylinderSensor, PlaneSensor, ProximitySensor, SphereSensor, TouchSensor, VisibilitySensor, or

Collision. See, Introduction to Sensors, for details.
3.37 geometry node

A node containing mathematical descriptions of three-dimensional (3D) Points, lines, surfaces, text strings and

solids. A node of type Box, Cone, Cylinder, ElevationGrid, Extrusion, IndexedFaceSet, IndexedLineSet, PointSet,

Sphere, or Text. See 4.6.3, Shapes and geometry, for details.
---------------------- Page: 13 ----------------------
ISO/IEC 14772=1:1997(E)
3.38 grab

To receive events from activated pointing devices (e.g., mause or Wann& A pointin,c device Sensor becomes the

exclusive recipient of pointing device events when one or more pointing devices are activated simultaneously.

3.39 gravity

In the context of ISOIIEC 14772, gravity may be simulated by constraining the motion of the viewpoint to the

lowest possible path (smallest Y-coordinate in the local coordinate System of the viewpoint) consistent with

following the surface of encountered obiects. See 6.29, NavigationInfo, for details.

3.40 grouping node

One of a set of node types which include a list of nodes, referred to as its children nodes. These children nodes are

collected together to share specific properties dependent on the type of the grouping node. Esch grouping node

defmes a coordinate space for its children relative to its own coordinate space. The children may themselves be

instances of grouping nodes, thus forming a transformation hierarchy. See 4.65 Grouping and children nodes, for

3.41 HSV
Hue, Saturation, and Value colour model. See E.[FOLEl.
3.42 HTML
HyperText Markup Language. See 2JHTMLl.
3.43 hyperlink

A reference to a URL that is associated with an Anchor node. See 6.2, Anchor, for details.

3.44 ideal VRML implementation

An implementation of VRML that presents all obiects and simulates movement without approximation. Not

realizable in practice.
3.45 IEC
International Electrotechnical Commission. See http : / /www . iec . ch.
3.46 IETF
Internet Engineering Task Forte. See
The organization which develops Internet Standards.
---------------------- Page: 14 ----------------------
0 ISOLIEC ISO/IEC 14772-1: 1997(E)
3.47 image

A two-dimensional (2D) rectangular array of Pixel values. Pixel values may have from one to four components. See

5.5, SFImage, for details.
3.48 in-lining
The mechanism by which one VRklL, {Ye is hierarchically included in another.
3.49 Internet

The world-wide named network of Computers which communicate with each other using a common set of

communication protocols known as TCP/IP. See /ETF. The World W& Weh is implemented on the Internet.

3.50 instance

A reference to a previously defined and named node. Nodes are named by means of the DEF Syntax and reference

by USE Syntax (see 4.6.2, DEFKJSE semantics). Instances of nodes may be used in any context in which the

defining node may be used.
3.51 interpolator node

A node that defines a piece-wise linear interpolation. A node of type ColorInterpolator, CoordinateInterpolator,

NormalInterpolator, OrientationInterpolator, PositionInterpolator, or ScalarInterpolator. See 4.6.8, hterpolator

nodes, for details.
3.52 intranet
A private network that uses the same protocols and Standards as the Internet.
3.53 ISO

International Organization for Standardization. See http: //

3.54 JPEG
Joint Photographit Experts Group. See 2. [JPEGl.
3.55 JTC 1
ISO/IEC Joint Technical Committee l.See
3.56 level of detail

The amount of detail or complexity which is displayed at any particular time for any particular Object. The level of

detail for an Object is controllable as a function of the distance of the Object from the viewer. See 6.26, LOD, for

details. (Abbreviated LOD)
---------------------- Page: 15 ----------------------
ISO/IEC 14772-1: 1997(E)
3.57 line terminator
A linefeed Character (OxOA) or a carriage retum Character (OxOD).
3.58 loop

A sequence of events which would result in a speciflc eventOut sending more than one event with the same

3.59 message

A data string sent between fyodes upon the occurrence of an event. See 4.10, Event processing, for details.

3.60 MIDI

Musical Instrument Digital Interface. A Standard for digital music representation. See 2.lMIDIl.

3.61 MIME

Multipurpose Internet Mai1 Extension. Used to specifl filetyping rules for lnteri7et applications, including br-owsers.

See 4.5.1, File extension and MIME types, for details. See also EJMIMEI.
3.62 mouse

A pointing device that moves in two dimensions and that enables a user to move a cursor on a display device in

Order to Point at displayed obiects. One or more push buttons on the mouse allow the user to indicate to the

Computer program that some action is to be taken.
3.63 MPEG
3.64 multimedia

An integrated presentation, typically on a Computer, of content of various types, such as Computer graphics, audio,

and Video.
3.65 network
Set of interconnected Computers.
3.66 node

The fundamental component of a Scene graph in ISO/IEC 14772. Nodes are abstractions of various real-world

objects and concepts. Examples include spheres, lights, and material descriptions. Nodes contairrfields and events.

Messages may be sent between nodes along routes.
---------------------- Page: 16 ----------------------
ISO/IEC 14772-1: 1997(E)
3.67 node type

A characteristic of each node that describes, in general, its particular semantics. For example, Box, Group, Sound,

and SpotLight are node types. See 4.6, Node semantics, and 6, Node reference, for details.

3.68 now
The present time as perceived by the User.
3.69 Object

A collection of data and procedures, packaged according to the rules and Syntax defined in ISO/IEC 14772. “Object”

is usually synonymous with node.
3.70 Object space
The coordinate System in which an Object is defined.
3.71 Panorama

A background texture that is placed behind all geometry in the Scene and in front of the ground and sky. See 6.5,

Background, for details.
3.72 parent
A node which is an instance of a grouping node.
3.73 PNG

Portable Network Graphits. A specification for representing two-dimensional images in fiZes. See 2.lPNGl.

3.74 pointer

A location and direction in the virtual world defmed by the pointing device which the user is currently using to

interact with the virtual world.
3.75 pointing device

A hardware device connected to the user ’s Computer by which the user directly controls the location and direction of

the pointer. Pointing devices may be either two-dimensional or three-dimensional and may have one or more control

buttons. See, Activating and manipulating Sensors, for details.
3.76 pointing device Sensor

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

SphereSensor, or TouchSensor. See
Anchor, CylinderSensor, PlaneSensor,
node of type, Pointing device Sensors, for details.
---------------------- Page: 17 ----------------------
ISO/PEC 14772=1:1997(E)
3.77 polyline

A sequence of straight line Segments where the end Point of the first Segment is coincident with the Start Point of the

second Segment, the endpoint of the second Segment is coincident with the Start Point of the third Segment, and so

on. A piecewise linear curve.
3.78 Profile

A named collection of criteria for functionality and conformance that defines an implementable subset of a Standard.

3.79 prototype

The definition of a new node tllpe in terms of the nodes defined in this part sf ISO/IEC 114772.

See 4.8, Prototype semantics, for details.
3.80 prototyping
The mechanism for extending the set of node types from within a VRML fZe.
3.81 public interface
The formal definition of a node type in this part of ISO/IEC 14772.
3.82 RGB

The colour model used within ISO/IEC 14772 for the specifkation of colours. Esch colour is represented as a

combination of the three primary colours red, green, and blue. See EJFOLEl.
3.83 route

The connection between a node generating an event and a node receiving the event. See 4.3.9, Route Statement

Syntax, and 4.10.2, Route semantics, for details.
3.84 route graph

The set of connections between eventOuts and evenths formed by ROUTE Statements or addRoute method

3.85 run-time name scope

The extent to which a name defmed within a VRML file applies and is visible. Several different run-time name

scopes are recognized and are defined in 4.4.6, Run-time name scope.
3.86 RURL
Relative Uniform Resource Locator. See 2. [RURLl.
---------------------- Page: 18 ----------------------
ISO/IEC 14772=1:1997(E)
3.87 Scene graph

An ordered collection of proupin,q nodes and other nodes. Grouping nodes, (such as LOD, Switch, and Transform

nodes) may have children nodes. See 4.23, Scene graph, and 4.4.2, Scene graph hierarchy, for details.

3.88 script

A set of procedural mnctions normally executed as part of an event cascade (see 6.40, Script). A script function may

also be executed asynchronously (see 4.12.6, Asynchronous scripts).
3.89 scripting
The process of creating or referring to a script.
3.90 scripting language

A System of syntactical and semantic constructs used to define and automate procedures and processes on a

Computer. Typically, scripting languages are interpreted and executed sequentially on a statement-by-Statement basis

whereas programming languages are generally compiled Prior to execution.
3.91 Sensor node

A node that enables the user to interact with the world in the Scene graph hierarchy. Sensor nodes respond to user

interaction with geometric obiticts in the world, the movement of the user through the world, or the passage of time.

See 4.6.7, Sensor nodes, for details.
3.92 separator Character

A UTF-8 Character used to separate syntactical entities in a VRML file. Specifically, commas, spaces, tabs, linefeeds,

and carriage-retums are separator characters wherever they appear outside of string Fjelds. See

4.3.1, Clear text (UTF-8) encoding, for details.
3.93 sibling
A node which shares aparent with other nodes.
3.94 Simulation tick
The smallest time unit capable of being identified in a digital S

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.