SIST EN ISO 16484-3:2005

Building automation and control systems (BACS) - Part 3: Functions (ISO 16484-3:2005)

This European Standard specifies the characteristics of software and functions used in Building automation and control systems as well as a method for documentation of the design. It gives guidelines for the engineering. It specifies a template for documentation of plant/application specific datapoints and functions, called BACS function list in annex A.
The informative function block examples explain a method to display the referenced functions in system documentation; they do not standardize the method for programming functions and applications.
This European  Standard covers the following:
Requirements and definitions regarding BACS and application software, generic function types for plant/project specific applications and engineering functions for building controls and operations. It provides communication functions for the integration of other dedicated special system processes. The functional requirements in this part of the standard are subdivided as follows:
-   System management and application software:
This clause describes the requirements for plant independent system and human system interface programs related to a project, including the operating system. This standard does not dedicate the following system functionality to any particular hardware, e.g.:
-   system diagnostics, watchdog, redundancy, time keeping, access control, log lists;
-   point identification, event message handling, print control;
-   database, statistics, data archiving, remote access;
-   system communications.
-   Human system interface (HSI), point information presentation, graphics, alarms, time scheduling
-   Engineering process and tool software:
This clause describes the requirements for configuring of the hardware and control strategies, the system management, and the commissioning process.
-   BACS application processing programs and plant/application specific function types:
This clause describes the requirements for plant, application, and / or project specific functi

Systeme der Gebäudeautomation (GA) - Teil 3: Funktionen (ISO 16484-3:2005)

Diese Internationale Norm legt die Merkmale der bei Systemen der Gebäudeautomation eingesetzten Software und Funktionen sowie ein Verfahren für die Dokumentation der Planung fest. Er gibt Leitlinien für die technische Bearbeitung. Er legt im Anhang A eine Vorlage für die Dokumentation der anlagen-/anwendungsspezifischen Datenpunkte und Funktionen, genannt GA-Funktionsliste, fest.
Die informativen (nicht normativen) Funktionsblock-Beispiele dienen nur zur Erläuterung eines Verfahrens, wie die entsprechenden Funktionen in einer Anlagendokumentation darstellbar sind; sie dienen nicht zur Normung der Vorgehensweise beim Programmieren von Funktionen und Anwendungen.
Diese Internationale Norm umfasst:
Definitionen und Anforderungen an ein GA-System und die Anwendungssoftware, Funktionen für anlagen-/projektspezifische Anwendungen und Engineering-Funktionen für die Automatisierung und den Betrieb von Gebäuden. Er beinhaltet Kommunikationsfunktionen für die Integration der Prozesse anderer Systeme für besondere Aufgaben. Die funktionalen Anforderungen in diesem Teil der Norm sind wie folgt unterteilt:
-   Systemmanagement- und Anwendungs-Software:
beschreibt die projektbezogenen Anforderungen an gewerkeunabhängige System-und  Mensch-System-Schnittstellenprogramme, einschließlich des Betriebssystems. Diese Norm ordnet die nachfolgenden Systemfunktionen nicht einer bestimmten Hardware zu:  
-   Systemdiagnose, Selbstüberwachung (watchdog), Redundanzsteuerung, Zeitverwaltung, Zugriffskontrolle zur Bedienfreigabe, Aktivitätenlisten;
-   Adressierungssystem für Benutzeradressen, Behandlung von Ereignismeldungen, Druckausgabesteuerung;
-   Datenbank, Statistiken, Datenarchivierung, Fernzugriff;
-   Systemkommunikation;
-   Mensch-System-Schnittstelle (MSS), Darstellung der Datenpunkt-Informationen, Grafiken, Alarmbehandlung, Zeitprogramm;

Systemes de gestion technique du bâtiment (SGTB) - Partie 3: Fonctions (ISO 16484-3:2005)

L'ISO 16484-3:2005 spécifie les exigences fonctionnelles d'ensemble, ainsi que les services d'ingénierie et de configuration, nécessaires à la réalisation de systèmes de gestion technique du bâtiment. Elle définit les termes à utiliser dans les documents de spécification et d'appel d'offres relatifs à un projet donné ou à une application particulière. Elle propose des lignes directrices pour la documentation fonctionnelle concernant les systèmes desdits projet ou application. Elle fournit un tableau de recensement des fonctions spécifiques à une installation/application, dénommé: «liste des objets SGTB».
Les exemples de blocs fonctionnels peuvent être réutilisés dans une documentation technique, afin d'illustrer le contenu normatif des fonctions référencées. Ils ne sauraient, par contre, être considérés comme une méthode standard décrivant la programmation de ces fonctions / applications.
L'ISO 16484-3:2005 couvre les exigences et définitions attachées aux SGTB et logiciels d'applications; fonctions génériques des applications spécifiques à une installation/un projet; fonctions de configuration pour les automatismes d'un bâtiment et son exploitation; fonctions référençant les objets de communication destinés à l'intégration de systèmes tiers dédiés.
L'ISO 16484-3:2005 définit une méthode de spécification des appels d'offres susceptibles de regrouper l'essentiel des éléments documentaires, nécessaires au bon fonctionnement opérationnel d'un SGTB. La garantie de succès d'un projet de SGTB, son bon déroulement et ses performances à l'exploitation, imposent au préalable que l'achat de prestations et d'équipements s'accorde à une spécification fonctionnelle complète et exacte.

Sistemi za avtomatizacijo in regulacijo stavb - 3. del: Funkcije (ISO 16484-3:2005)

General Information

• Status: Published
• Publication Date: 28-Feb-2005
• ICS: 35.240.67 - IT applications in building and construction industry
• ICS: 97.120 - Automatic controls for household use
• Technical Committee: OGS - Heating for buildings
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Mar-2005
• Due Date: 01-Mar-2005
• Completion Date: 01-Mar-2005
• Ref Project: EN ISO 16484-3:2005 - Building automation and control systems (BACS) - Part 3: Functions (ISO 16484-3:2005)

Relations

• Splited From: oSIST prEN ISO 16484-2:2016 - Building automation and control systems (BACS) - Part 2: Hardware (ISO/DIS 16484-2:2016)
• Effective Date: 08-Mar-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 16484-3:2005
01-marec-2005
Sistemi za avtomatizacijo in regulacijo stavb - 3. del: Funkcije (ISO 16484-3:2005)
Building automation and control systems (BACS) - Part 3: Functions (ISO 16484-3:2005)
Systeme der Gebäudeautomation (GA) - Teil 3: Funktionen (ISO 16484-3:2005)
Systemes de gestion technique du bâtiment (SGTB) - Partie 3: Fonctions (ISO 16484-
3:2005)
Ta slovenski standard je istoveten z: EN ISO 16484-3:2005
ICS:
35.240.67 Uporabniške rešitve IT v IT applications in building
gradbeništvu and construction industry
97.120 Avtomatske krmilne naprave Automatic controls for
za dom household use
SIST EN ISO 16484-3:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 16484-3:2005

---------------------- Page: 2 ----------------------
SIST EN ISO 16484-3:2005
EUROPEAN STANDARD
EN ISO 16484-3
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2005
ICS 35.240.99; 97.120
English version
Building automation and control systems (BACS) - Part 3:
Functions (ISO 16484-3:2005)
Systèmes de gestion technique du bâtiment (SGTB) - Systeme der Gebäudeautomation (GA) - Teil 3: Funktionen
Partie 3: Fonctions (ISO 16484-3:2005) (ISO 16484-3:2005)
This European Standard was approved by CEN on 10 December 2003.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16484-3:2005: E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
Contents
page
Foreword .4
Introduction.5
1 Scope.8

2 Normative references .9
3 Terms and definitions.9
4 Symbols, abbreviations and acronyms.9
5 Requirements.9
5.1 Overview.9
5.1.1 Structure of the requirements and functions.9
5.1.2 Description of functions.11
5.1.3 Description of function block examples .12
5.1.4 Description of the BACS function list .12
5.2 General system criteria .12
5.3 Software.13
5.3.1 BACS programs general.13
5.3.2 System management programs.13
5.3.3 Communication programs.17
5.3.4 BACS application programs.19
5.3.5 Human system interface programs .20

5.3.6 Service and commissioning functions.26
5.3.7 Operating system.27
5.4 System engineering programs.28
5.4.1 General description of the engineering process .28
5.4.2 Project specific system design.28
5.4.3 Hardware configuration.28
5.4.4 Control strategy configuration.29
5.4.5 Management and operator functions configuration.30
5.4.6 Commissioning tool.30
5.5 BACS function types .31
5.5.1 General requirements for BACS functions .31
5.5.2 I/O function types.31
5.5.3 Processing function types .34
5.5.4 Management function types.62
5.5.5 Operator function types .64
Annex A (normative) BACS function list (BACS FL) .66
A.1 Use of the BACS FL .66
A.1.1 Functions in the BACS FL.66
A.1.2 Structure of the BACS FL.66
A.1.3 Describing applications by functions of the BACS FL.66
A.1.4 Advice about the application of function types.67
A.1.5 Additional specifications.67
A.1.6 Describing system integration with functions.67
A.2 BACS function list template.68
(informative)
Annex B Examples for control schematics and BACS function lists .70
B.1 Example 1, AHU .70
B.1.1 Abbreviations used in example 1 .70
B.1.2 Example 1, Control schematic and BACS FL.70
B.2 Example 2, energy plant .74
B.2.1 Abbreviations used in example 2 .74
B.2.2 Example 2, plant schematic .75
B.2.3 Example 2, plant description.75
2

---------------------- Page: 4 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
B.2.4 Example 2, controls description .76
B.2.5 Example 2, Control flow chart diagram .77
B.2.6 Example 2, BACS function list.80
Annex C (informative) Bibliography.82
Annex ZA (normative)  Normative references to international publications with their corresponding
European publications .83

3

---------------------- Page: 5 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
Foreword

This International Standard (EN ISO 16484-3:2005) has been prepared by Technical Committee CEN /TC 247,
"Building Automation, Controls and Building Management", the secretariat of which is held by the SNV, in
collaboration with ISO/TC 205 "Building Environment Design".
This International Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by January 2006, and conflicting national standards shall be withdrawn at
the latest by January 2006.

The EN ISO 16484-3 is part of the EN ISO 16484 series of International Standards under the general title
Building Automation and Control Systems (BACS), which will comprise the following parts:
Part 1: Overview and definitions
Part 2: Hardware
Part 3: Functions
Part 4: Applications
Part 5: Data communication protocol
Part 6: Data communication - Conformance testing
Part 7: Project specification and implementation

Annex A (normative): BACS function list, forms a normative part of this standard.
The Annex B (informative): Examples for plant-/control schematic and BACS function list, and
Annex C (informative): bibliography, are for information only.
The Annex ZA (normative): Normative references to international publications with the corresponding European
publications, is normative part of this International Standard.
NOTE  National annexes may contain information provided for easier implementation of the standard, e.g. an alphabetical
index or national footnotes.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this International Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
4

---------------------- Page: 6 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
Introduction
This series of standards is intended for design of new buildings and retrofit of existing buildings for an acceptable
indoor environment, practical energy conservation, and efficiency.
The application of this series of standards for BACS is envisaged as follows:
- the environmental design for all building types requires complex methods for automation and control. The
functional integration of services other than HVAC is a general task for all parties employed to develop an
integrated multi-application system. The Integration comprises, e.g. lighting and electric power distribution
control, security control, transportation, maintenance management, or facilities management. This system
integration allows the user to take advantage of synergies between the different applications. This standard will
give guidance to architects, consultants, and contractors as well as to users on how to share such resources;
- the innovation cycles between devices, systems, and networks vary. To make it possible to add and to change
existing devices, and extend the building automation and control network, several interfaces both proprietary and
standardized are defined between the BACS network and the other systems. A manufacturer can design a
product, both to meet his specific marketing objectives and to give the option to integrate that special device into
a multi-application BACS. Interfaces are also defined in appropriate parts of this standard along with the
necessary communications protocol and conformance test required to support the inter-working of devices;
- a manufacturer, a systems house, or an electrical or mechanical contractor can assemble an implementation of
a building automation and control system;
- the application of this standard is not to standardize the hardware and software design or the architecture of a
System, but to define the process for the creation of project specifications, where functionality and the quality of
the solution are clearly defined.
The purpose of this series of standards is intended for use by those involved in the design, manufacture,
engineering, installation, commissioning, operational maintenance and training of BACS when contracted, i.e.:
 as a guide to the terminology of the building automation and control trade. Unambiguous terminology is
required for a complete and accurate conveyance of the intent and details of this standard;
in product development, to avoid unnecessary duplication of function or terminology, but should not place a

restraint on the evolution of new products, systems or applications;
 as a basis for interfacing products and systems. In order to interoperate, the elements of a BACS require a
unified data communication protocol and information model;
 as a basis for drawing up a project specification for the procurement of building automation and control
products for systems suppliers and customers;
 as a code of practice for expertly commissioning prior to handover of a system;
 by educational establishments wishing to train people in the field of building automation and control systems.
This entire series of BACS standards consists of the following contents:
Part 1: Overview and definitions (in preparation)
Part 1 of this standard describes the objectives and interrelationships of all parts of this standard. It provides an
overview and detailed information about the structure of the related series of standards for the BACS industry.
This part of the standard provides also the vocabulary with terms and definitions for the understanding of the
entire series of this standard and it contains a translation of the main terms in English, French, Russian, and
German in an informative annex.
This ongoing work is coordinated at expert level with standards work from ISO/TC 205 WG 3 and CEN/TC 247/
WG 3, WG 4 WG 5 and WG 6.
5

---------------------- Page: 7 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
Part 2: Hardware
Part 2 of this standard specifies the requirements for the hardware to perform the tasks within a BACS. It
provides the terms, definitions, and abbreviations for the understanding of Part 2 and Part 3.
Part 2 relates only to physical items/devices, i.e.:
 operator stations and other human system interface devices;
devices for management functions;

 control devices, automation stations and application specific controllers;
 field devices and their interfaces;
 cabling and interconnection of devices;
engineering and commissioning tools.

This part of this standard shows a generic system model to which all-different types of BACS and their
interconnections (BACS network) can fit. A graphical concept of the BACS network in terms of LAN and inter-
network topology will be provided in Part 5 of this standard.
National annexes:
National annexes may specify the local requirements of physical and electrical characteristics, the verifications
for BACS devices and equipment, and the code of practice for the physical installation of systems. The annexes
shall refer to the regional implementations of the relevant IEC standards.
Part 3: Functions (refer to the scope of this part)
Part 4: Applications
Part 4 of this standard specifies the requirements for specific communicating applications/devices, e.g. for
general room automation and for sophisticated optimization of controls for heating, fan coil and induction units,
CAV, VAV and radiant cooling.
This work will be coordinated at expert level with standards work from ISO/TC 205 WG 3 and CEN/TC 247.
Part 5: Data Communication – Protocol
Part 5 of this standard specifies data communication services and objects for computer equipment and
controllers used for monitoring and control of HVAC&R and other systems of building services.
This protocol provides a comprehensive set of object types for conveying encoded binary, analog, and
alphanumeric data between devices including, but not limited to:
 input measuring: analog input object;
 output positioning/setpoint: analog output object;
 binary input counting;
 input state: binary input object, multi-state input;
 output switching: binary output object, multi-state output;
 values: analog value, binary value, multi-state value, accumulated value, averaging object, trend log object;
 text string;
 schedule information;
6

---------------------- Page: 8 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
 alarm and event information;
 files; and
 control programs and parameters respectively.
This protocol models each building automation and control system as a collection of data structures called object
types, the properties of which represent various aspects of the hardware, software, and operation of the device.
These objects provide a means of identifying and accessing information without requiring knowledge of the
details of the device's internal design or configuration.
NOTE  An overview of possible integration with other systems in buildings, e.g. fire, security, access control, maintenance
and facilities management, is shown in Figure 1 of Part 2 of this standard.
Part 6: Data Communication – Conformance testing (in preparation)

Part 6 of this standard specifies the technical requirements of the conformance test suite and the methods for
testing the products for the conformance with the protocol. It provides a comprehensive set of procedures for
verifying the correct implementation of each capability claimed on a BACS network protocol implementation
conformance statement (PICS) including:
 support of each claimed BACS network service, either as a client (initiator), server (executor), or both;
 support of each claimed BACS network object-type, including both required properties and each claimed
optional property;
 support of the BACS network layer protocol;
 support of each claimed data link option, and
 support of all claimed special functionality.
Part 7: Project implementation
Part 7 of this standard specifies methods for project specification and implementation of BACS and for
integration of other systems into the BACS. This standard defines terms to be used for project specifications and
gives guidelines for integration of other systems.
a) Project specification and implementation:
This clause of the standard describes the procedures (codes of practice) required for the following:
 project specification:
These procedures also contain an example for a plant/system/customer premises wide unique
structured addressing system for data point identification;
 engineering;
 installation;
 project handover.
b) System integration:
This clause of the standard describes the special requirements/procedures for the integration and
implementation of intersystem communication with foreign systems and the interconnection of other
units/devices with integrated communications interfaces, e.g. chillers, elevators.
7

---------------------- Page: 9 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
1 Scope
This International Standard specifies the characteristics of software and functions used in Building automation
and control systems as well as a method for documentation of the design. It gives guidelines for the engineering.
It specifies a template for documentation of plant/application specific datapoints and functions, called BACS
function list in annex A.
The informative function block examples explain a method to display the referenced functions in system
documentation; they do not standardize the method for programming functions and applications.
This International Standard covers the following:
Requirements and definitions regarding BACS and application software, generic function types for plant/project
specific applications and engineering functions for building controls and operations. It provides communication
functions for the integration of other dedicated special system processes. The functional requirements in this part
of the standard are subdivided as follows:
 System management and application software:
This clause describes the requirements for plant independent system and human system interface programs
related to a project, including the operating system. This standard does not dedicate the following system
functionality to any particular hardware, e.g.:
 system diagnostics, watchdog, redundancy, time keeping, access control, log lists;
 point identification, event message handling, print control;
 database, statistics, data archiving, remote access;
 system communications.
 Human system interface (HSI), point information presentation, graphics, alarms, time scheduling
 Engineering process and tool software:
This clause describes the requirements for configuring of the hardware and control strategies, the system
management, and the commissioning process.
 BACS application processing programs and plant/application specific function types:
This clause describes the requirements for plant, application, and / or project specific functions and a method for
the documentation of a project. The functions are subdivided into the following types:
 input and output functions;
 processing functions;
 management functions and required communications;
operator functions.

This International Standard defines a method for creating the procurement specifications containing all essential
elements required for the operational functioning of a BACS. The successful installation and operation of a
BACS requires that its procurement be based on a complete specification with accurate functions.
The standard provides a template called the ‘BACS function list’ that can be found in annex A (normative). Its
purpose is to determine and document the options for plant / application specific functionality. Further
explanations can be given in form of plant/control descriptions, control flow chart diagrams, and plant/control
schematics. Examples are given in annex B (informative). The exact specifications will be project-specific.
Information about the standardized functions is given in the form of informative examples as function-blocks,
textual, and graphical descriptions in 5.5.
8

---------------------- Page: 10 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
It is recognized, that functions can be described and implemented in many different ways, depending on:
 climatic differences;
 cultural and regional differences;
 national regulations.
2 Normative references
The following referenced documents are indispensable for the application of this International Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN ISO 10628:2000 Flow diagrams for process plants — General rules (ISO 10628:1997)
EN ISO 16484-2:2004
Building automation and control systems (BACS) — Part 2: Hardware (ISO 16484-
2:2004)
EN ISO 16484-5
Building automation and control systems (BACS) — Part 5: Data communication
protocol (ISO 16484-5:2003)
IEC 60617-12:1997 Graphical symbols for diagrams — Part 12: Binary logic elements (IEC 60617-
12:1997)
IEC 60617-13:1993 Graphical symbols for diagrams — Part 13: Analogue elements (IEC 60617-13:1993
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in EN ISO 16484-2:2004 apply.
4 Symbols, abbreviations and acronyms
For the purposes of this standard, the symbols, abbreviations and acronyms given in EN ISO 16484-2:2004
apply.
NOTE  The abbreviations used and explained within the tables for the function block examples are for information only.
5 Requirements
5.1 Overview
5.1.1 Structure of the requirements and functions
5.1.1.1 General
This standard does not dedicate the system functionality to any particular hardware. The functional requirements
in this part of the standard are subdivided as follows:
 system application and management software:
describes the requirements for plant independent system programs and human system interface programs
related to a project in general;
 engineering and commissioning tools:
9

---------------------- Page: 11 ----------------------
SIST EN ISO 16484-3:2005
EN ISO 16484-3:2005(E)
describes the requirements for the configuration of hardware, of control strategies and management
functions,
and the commissioning process;
 project/plant specific functions:
describes the requirements for plant applications and/or project specific functions and methods for the
functional documentation of project and/or application specific systems.
The functions of a BACS in general are structured into three levels. These levels indicate functions for
 management,
 automation/control as processing functions, and
 input/output as interface to field devices.
Operator functions are not assigned to a specific level.
NOTE  Requirements for the hardware and communication means to perform the BACS software and functions that are
specified in Part 2 of this standard.
5.1.1.2 Operator functions
Human system interface for plant operation, i.e. for supervision, alarm annunciation, state monitoring and human
interaction are not assigned to any functional level.
The range of functionality covers:
a) system management, event management and state management, parameter adjustment and manual on/off
control;
b) local room operation;
c) local override/indication device functions to provide restricted access for service operation;
d) system engineering and servicing, engineered operator functions are, e.g. dynamic display, event instruction
text, remote messaging (see 5.5.5).
NOTE  Human system interface devices in a BACS are on different types of hardware, as specified in Part 2:
- direct acting elements, as switches and signal lights;
- local override and/or indication devices;
- handheld units;
- monitoring and operator units or panels;
- operator stations including visual display units and
- Internet based browsers.
A VDU can provide a graphical user interfa
...