IEC 61158-5-4:2014

IEC 61158-5-4 ®
Edition 2.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Fieldbus specifications –
Part 5-4: Application layer service definition – Type 4 elements

Réseaux de communication industriels – Spécifications des bus de terrain –
Partie 5-4: Définition des services de la couche application – Eléments de type 4

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IEC 61158-5-4 ®
Edition 2.0 2014-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Industrial communication networks – Fieldbus specifications –

Part 5-4: Application layer service definition – Type 4 elements

Réseaux de communication industriels – Spécifications des bus de terrain –

Partie 5-4: Définition des services de la couche application – Eléments de type 4

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XB
ICS 25.040.40; 35.100.70; 35.110 ISBN 978-2-8322-1733-7

– 2 – IEC 61158-5-4:2014 © IEC 2014

CONTENTS
FOREWORD . 4

INTRODUCTION . 6

1 Scope . 7

1.1 General . 7

1.2 Specifications . 8

1.3 Conformance . 8

2 Normative references . 8

3 Terms and definitions . 9
3.1 ISO/IEC 7498-1 terms . 9
3.2 ISO/IEC 8822 terms . 9
3.3 ISO/IEC 9545 terms . 9
3.4 ISO/IEC 8824-1 terms . 10
3.5 Fieldbus data-link layer terms . 10
3.6 Fieldbus application layer specific definitions . 10
3.7 Abbreviations and symbols . 16
3.8 Conventions . 17
4 Concepts . 20
4.1 Overview . 20
4.2 Architectural relationships . 21
4.3 Fieldbus Application Layer structure . 23
4.4 Fieldbus Application Layer naming and addressing . 35
4.5 Architecture summary . 35
4.6 FAL service procedures . 36
4.7 Common FAL attributes . 37
4.8 Common FAL service parameters . 37
4.9 APDU size . 38
5 Type 4 communication model specification . 38
5.1 Concepts . 38
5.2 Variable ASE . 45
5.3 Application relationship ASE . 64
Bibliography . 71

Figure 1 – Relationship to the OSI basic reference model . 21
Figure 2 – Architectural positioning of the fieldbus Application Layer . 22
Figure 3 – Client/server interactions . 24
Figure 4 – Pull model interactions . 25
Figure 5 – Push model interactions . 26
Figure 6 – APOs services conveyed by the FAL . 27
Figure 7 – Application entity structure . 29
Figure 8 – Example FAL ASEs . 30
Figure 9 – FAL management of objects . 31
Figure 10 – ASE service conveyance . 32
Figure 11 – Defined and established AREPs . 34
Figure 12 – FAL architectural components . 36

Figure 13 – FAL AE . 39

Figure 14 – Summary of the FAL architecture . 42

Figure 15 – FAL service procedure overview. 43

Figure 16 – Time sequence diagram for the confirmed services . 44

Figure 17 – Time sequence diagram for unconfirmed services . 45

Table 1 – REQUEST service parameters . 60

Table 2 – RESPONSE service parameters . 61

Table 3 – Error codes by source . 62
Table 4 – Reserve REP service parameters . 62
Table 5 – Free AREP service parameters . 63
Table 6 – Get REP attribute service parameters . 63
Table 7 – Set REP attribute service parameters . 64
Table 8 – AR send service parameters . 68
Table 9 – AR acknowledge service parameters . 68
Table 10 – AR get attributes service parameters . 69
Table 11 – AR set attributes service parameters . 69

– 4 – IEC 61158-5-4:2014 © IEC 2014

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 5-4: Application layer service definition –

Type 4 elements
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
Attention is drawn to the fact that the use of the associated protocol type is restricted by its
intellectual-property-right holders. In all cases, the commitment to limited release of
intellectual-property-rights made by the holders of those rights permits a layer protocol type to
be used with other layer protocols of the same type, or in other type combinations explicitly
authorized by its intellectual-property-right holders.
NOTE Combinations of protocol types are specified in IEC 61784-1 and IEC 61784-2.
International Standard IEC 61158-5-4 has been prepared by subcommittee 65C: Industrial
networks, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 2007. This edition
constitutes an editorial revision with only minor editorial changes.

This edition includes the following significant changes with respect to the previous edition:

a) editorial improvements;
b) editorial corrections.
The text of this standard is based on the following documents:

FDIS Report on voting
65C/763/FDIS 65C/773/RVD
Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.
This publication has been drafted in accordance with ISO/IEC Directives, Part 2.
A list of all the parts of the IEC 61158 series, under the general title Industrial communication
networks – Fieldbus specifications, can be found on the IEC web site.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under http://webstore.iec.ch in the data related
to the specific publication . At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 61158-5-4:2014 © IEC 2014

INTRODUCTION
This part of IEC 61158 is one of a series produced to facilitate the interconnection of

automation system components. It is related to other standards in the set as defined by the

“three-layer” fieldbus reference model described in IEC 61158-1.

The application service is provided by the application protocol making use of the services

available from the data-link or other immediately lower layer. This standard defines the

application service characteristics that fieldbus applications and/or system management may

exploit.
Throughout the set of fieldbus standards, the term “service” refers to the abstract capability
provided by one layer of the OSI Basic Reference Model to the layer immediately above.
Thus, the application layer service defined in this standard is a conceptual architectural
service, independent of administrative and implementation divisions.

INDUSTRIAL COMMUNICATION NETWORKS –

FIELDBUS SPECIFICATIONS –
Part 5-4: Application layer service definition –

Type 4 elements
1 Scope
1.1 General
The fieldbus application layer (FAL) provides user programs with a means to access the
fieldbus communication environment. In this respect, the FAL can be viewed as a “window
between corresponding application programs.”
This standard provides common elements for basic time-critical and non-time-critical
messaging communications between application programs in an automation environment and
material specific to Type 4 fieldbus. The term “time-critical” is used to represent the presence
of a time-window, within which one or more specified actions are required to be completed
with some defined level of certainty. Failure to complete specified actions within the time
window risks failure of the applications requesting the actions, with attendant risk to
equipment, plant and possibly human life.
This standard defines in an abstract way the externally visible service provided by the Type 4
fieldbus application layer in terms of
a) an abstract model for defining application resources (objects) capable of being
manipulated by users via the use of the FAL service,
b) the primitive actions and events of the service;
c) the parameters associated with each primitive action and event, and the form which they
take; and
d) the interrelationship between these actions and events, and their valid sequences.
The purpose of this standard is to define the services provided to
1) the FAL user at the boundary between the user and the application layer of the fieldbus
reference model, and
2) Systems Management at the boundary between the application layer and Systems

Management of the fieldbus reference model.
This standard specifies the structure and services of the Type 4 fieldbus application layer, in
conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application
layer structure (ISO/IEC 9545).
FAL services and protocols are provided by FAL application-entities (AE) contained within the
application processes. The FAL AE is composed of a set of object-oriented application service
elements (ASEs) and a layer management entity (LME) that manages the AE. The ASEs
provide communication services that operate on a set of related application process object
(APO) classes. One of the FAL ASEs is a management ASE that provides a common set of
services for the management of the instances of FAL classes.
Although these services specify, from the perspective of applications, how request and
responses are issued and delivered, they do not include a specification of what the requesting
and responding applications are to do with them. That is, the behavioral aspects of the
applications are not specified; only a definition of what requests and responses they can

– 8 – IEC 61158-5-4:2014 © IEC 2014

send/receive is specified. This permits greater flexibility to the FAL users in standardizing

such object behavior. In addition to these services, some supporting services are also defined

in this standard to provide access to the FAL to control certain aspects of its operation.

1.2 Specifications
The principal objective of this standard is to specify the characteristics of conceptual

application layer services suitable for time-critical communications, and thus supplement the

OSI Basic Reference Model in guiding the development of application layer protocols for time-
critical communications.
A secondary objective is to provide migration paths from previously-existing industrial
communications protocols. It is this latter objective which gives rise to the diversity of services
standardized as the various Types of IEC 61158, and the corresponding protocols
standardized in IEC 61158-6 series.
This specification may be used as the basis for formal application programming interfaces.
Nevertheless, it is not a formal programming interface, and any such interface will need to
address implementation issues not covered by this specification, including
a) the sizes and octet ordering of various multi-octet service parameters, and
b) the correlation of paired request and confirm, or indication and response, primitives.
1.3 Conformance
This standard does not specify individual implementations or products, nor does it constrain
the implementations of application layer entities within industrial automation systems.
There is no conformance of equipment to this application layer service definition standard.
Instead, conformance is achieved through implementation of conforming application layer
protocols that fulfill the Type 2 application layer services as defined in this standard.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
NOTE All parts of the IEC 61158 series, as well as IEC 61784-1 and IEC 61784-2 are maintained simultaneously.
Cross-references to these documents within the text therefore refer to the editions as dated in this list of normative
references.
IEC 61158-3-4:2014, Industrial communication networks – Fieldbus specifications – Part 3-4:
Data-link layer service definition – Type 4 elements
IEC 61158-4-4:2014, Industrial communication networks – Fieldbus specifications – Part 4-4:
Data-link layer protocol specification – Type 4 elements
IEC 61158-6-4:2014, Industrial communication networks – Fieldbus specifications – Part 6-4:
Application layer protocol specification – Type 4 elements
IEC 61158-6 (all subparts), Industrial communication networks – Fieldbus specifications –
Part 6: Application layer protocol specification
ISO/IEC 7498-1, Information technology – Open Systems Interconnection – Basic Reference
Model – Part 1: The Basic Model

ISO/IEC 7498-3, Information technology – Open Systems Interconnection – Basic Reference

Model – Part 3: Naming and addressing

ISO/IEC 8822, Information technology – Open Systems Interconnection – Presentation

service definition
ISO/IEC 8824-1, Information technology – Abstract Syntax Notation One (ASN.1):

Specification of basic notation

ISO/IEC 9545, Information technology – Open Systems Interconnection – Application Layer

structure
ISO/IEC 10731, Information technology – Open Systems Interconnection – Basic Reference
Model – Conventions for the definition of OSI services
ISO/CEI/IEEE 60559, Information technology – Microprocessor Systems – Floating-Point
arithmetic
3 Terms and definitions
For the purposes of this document, the following terms as defined in these publications apply:
3.1 ISO/IEC 7498-1 terms
a) application entity
b) application process
c) application protocol data unit
d) application service element
e) application entity invocation
f) application process invocation
g) application transaction
h) real open system
i) transfer syntax
3.2 ISO/IEC 8822 terms
For the purposes of this document, the following terms as defined in ISO/IEC 8822 apply:
a) abstract syntax
b) presentation context
3.3 ISO/IEC 9545 terms
For the purposes of this document, the following terms as defined in ISO/IEC 9545 apply:
a) application-association
b) application-context
c) application context name
d) application-entity-invocation
e) application-entity-type
f) application-process-invocation

– 10 – IEC 61158-5-4:2014 © IEC 2014

g) application-process-type
h) application-service-element

i) application control service element

3.4 ISO/IEC 8824-1 terms
For the purposes of this document, the following terms as defined in ISO/IEC 8824-1 apply:

a) object identifier
b) type
3.5 Fieldbus data-link layer terms
For the purposes of this document, the following terms apply.
a) DL-Time
b) DL-Scheduling-policy
c) DLCEP
d) DLC
e) DLPDU
f) DLSDU
g) DLSAP
h) fixed tag
i) generic tag
j) link
k) network address
l) node address
m) node
n) tag
o) scheduled
p) unscheduled
3.6 Fieldbus application layer specific definitions
For the purposes of this standard, the following terms and definitions apply.
3.6.1
application
function or data structure for which data is consumed or produced
3.6.2
application objects
multiple object classes that manage and provide a run time exchange of messages across the
network and within the network device
3.6.3
application process
part of a distributed application on a network, which is located on one device and
unambiguously addressed
3.6.4
application process identifier
distinguishes multiple application processes used in a device

3.6.5
application process object
component of an application process that is identifiable and accessible through an FAL

application relationship
Note 1 to entry:  Application process object definitions are composed of a set of values for the attributes of their
class (see the definition for Application Process Object Class Definition). Application process object definitions
may be accessed remotely using the services of the FAL Object Management ASE. FAL Object Management

services can be used to load or update object definitions, to read object definitions, and to dynamically create and

delete application objects and their corresponding definitions.

3.6.6
application process object class

class of application process objects defined in terms of the set of their network-accessible
attributes and services
3.6.7
application relationship
cooperative association between two or more application-entity-invocations for the purpose of
exchange of information and coordination of their joint operation
Note 1 to entry:  This relationship is activated either by the exchange of application-protocol-data-units or as a
result of preconfiguration activities.
3.6.8
application relationship application service element
application-service-element that provides the exclusive means for establishing and
terminating all application relationships
3.6.9
application relationship endpoint
context and behavior of an application relationship as seen and maintained by one of the
application processes involved in the application relationship
Note 1 to entry:  Each application process involved in the application relationship maintains its own application
relationship endpoint.
3.6.10
attribute
description of an externally visible characteristic or feature of an object
Note 1 to entry:  The attributes of an object contain information about variable portions of an object. Typically, they
provide status information or govern the operation of an object. Attributes may also affect the behaviour of an
object. Attributes are divided into class attributes and instance attributes.

3.6.11
behaviour
indication of how an object responds to particular events
3.6.12
bit-no
designates the number of a bit in a bitstring or an octet
3.6.13
channel
single physical or logical link of an input or output application object of a server to the process

– 12 – IEC 61158-5-4:2014 © IEC 2014

3.6.14
class
set of objects, all of which represent the same kind of system component

Note 1 to entry:  A class is a generalisation of an object; a template for defining variables and methods. All objects

in a class are identical in form and behaviour, but usually contain different data in their attributes.

3.6.15
class attributes
attribute that is shared by all objects within the same class

3.6.16
class code
unique identifier assigned to each object class
3.6.17
class specific service
service defined by a particular object class to perform a required function which is not
performed by a common service
Note 1 to entry:  A class specific object is unique to the object class which defines it.
3.6.18
client
a) object which uses the services of another (server) object to perform a task
b) initiator of a message to which a server reacts
3.6.19
communication objects
components that manage and provide a run time exchange of messages across the network
EXAMPLES: Connection Manager object, Unconnected Message Manager (UCMM) object, and Message Router
object.
3.6.20
connection
logical binding between application objects that may be within the same or different devices
Note 1 to entry: Connections may be either point-to-point or multipoint.
3.6.21
conveyance path
unidirectional flow of APDUs across an application relationship

3.6.22
dedicated AR
AR used directly by the FAL User
Note 1 to entry:  On Dedicated ARs, only the FAL Header and the user data are transferred.
3.6.23
default DL-address
value 126 as an initial value for DL-address, which has to be changed (e.g. by assignment of
a DL-address via the fieldbus) before operation with a DP-master (class 1)
3.6.24
device
physical hardware connected to the link
Note 1 to entry:  A device may contain more than one node.

3.6.25
dynamic AR
AR that requires the use of the AR establishment procedures to place it into an established

state
3.6.26
endpoint
one of the communicating entities involved in a connection

3.6.27
error
discrepancy between a computed, observed or measured value or condition and the specified
or theoretically correct value or condition
3.6.28
error class
general grouping for related error definitions and corresponding error codes
3.6.29
error code
identification of a specific type of error within an error class
3.6.30
event
instance of a change of conditions
3.6.31
FAL subnet
subnetworks composed of one or more data link segments, identified by a subset of the
network address
Note 1 to entry:  FAL subnets are permitted to contain bridges but not routers.
3.6.32
FIFO variable
Variable Object class, composed of a set of homogeneously typed elements, where the first
written element is the first element that can be read
Note 1 to entry:  On the fieldbus only one, complete element can be transferred as a result of one service
invocation.
3.6.33
frame
denigrated synonym for DLPDU
3.6.34
interface
a) shared boundary between two functional units, defined by functional characteristics, signal
characteristics, or other characteristics as appropriate
b) collection of FAL class attributes and services that represents a specific view on the FAL
class
– 14 – IEC 61158-5-4:2014 © IEC 2014

3.6.35
invocation
act of using a service or other resource of an application process

Note 1 to entry:  Each invocation represents a separate thread of control that may be described by its context.

Once the service completes, or use of the resource is released, the invocation ceases to exist. For service
invocations, a service that has been initiated but not yet completed is referred to as an outstanding service

invocation. Also for service invocations, an Invoke ID may be used to unambiguously identify the service invocation

and differentiate it from other outstanding service invocations.

3.6.36
index
address of an object within an application process

3.6.37
instance
actual physical occurrence of an object within a class that identifies one of many objects
within the same object class
EXAMPLE California is an instance of the object class state.
Note 1 to entry:  The terms object, instance, and object instance are used to refer to a specific instance.
3.6.38
instance attributes
attribute that is unique to an object instance and not shared by the object class
3.6.39
instantiated
object that has been created in a device
3.6.40
logical device
certain FAL class that abstracts a software component or a firmware component as an
autonomous self-contained facility of an automation device
3.6.41
manufacturer ID
identification of each product manufacturer by a unique number
3.6.42
management information
network-accessible information that supports managing the operation of the fieldbus system,
including the application layer

Note 1 to entry:  Managing includes functions such as controlling, monitoring, and diagnosing.
3.6.43
member
piece of an attribute that is structured as an element of an array
3.6.44
method
a synonym for an operational service which is provided by the server ASE and
invoked by a client
3.6.45
module
hardware or logical component of a physical device

3.6.46
network
set of nodes connected by some type of communication medium, including any intervening

repeaters, bridges, routers and lower-layer gateways

3.6.47
object
abstract representation of a particular component within a device, usually a collection of

related data (in the form of variables) and methods (procedures) for operating on that data

that have clearly defined interface and behaviour

3.6.48
object specific service
service unique to the object class which defines it
3.6.49
peer
role of an AR endpoint in which it is capable of acting as both client and server
3.6.50
physical device
automation or other network device
3.6.51
property
general term for descriptive information about an object
3.6.52
provider
source of a data connection
3.6.53
publisher
role of an AR endpoint that transmits APDUs onto the fieldbus for consumption by one or
more subscribers
Note 1 to entry:  A publisher may not be aware of the identity or the number of subscribers and it may publish its
APDUs using a dedicated AR.
3.6.54
publishing manager
role of an AR endpoint in which it issues one or more confirmed service request APDUs to a

publisher to request the publisher to publish a specified object
Note 1 to entry:  Two types of publishing managers are defined by this standard, pull publishing managers and
push publishing managers, each of which is defined separately
3.6.55
pull subscriber
type of subscriber that recognizes received confirmed service response APDUs as published
object data
3.6.56
resource
processing or information capability of a subsystem
3.6.57
route endpoint
object container containing Variable Objects of a variable class

– 16 – IEC 61158-5-4:2014 © IEC 2014

3.6.58
server
a) role of an AREP in which it returns a confirmed service response APDU to the client that

initiated the request
b) object which provides services to another (client) object

3.6.59
service
operation or function than an object and/or object class performs upon request from another

object and/or object class
3.6.60
subscriber
role of an AREP in which it receives APDUs produced by a publisher
3.7 Abbreviations and symbols
AE Application Entity
AL Application Layer
ALME Application Layer Management Entity
ALP Application Layer Protocol
APO Application Object
AP Application Process
APDU Application Protocol Data Unit
API Application Process Identifier
AR Application Relationship
AREP Application Relationship End Point
ASCII American Standard Code for Information Interchange
ASE Application Service Element
Cnf Confirmation
CR Communication Relationship
CREP Communication Relationship End Point
DL- (as a prefix) Data Link-
DLC Data Link Connection
DLCEP Data Link Connection End Point
DLL Data Link Layer
DLM Data Link-management
DLSAP Data Link Service Access Point
DLSDU DL-service-data-unit
DNS Domain Name Service
DP Decentralised Peripherals
FAL Fieldbus Application Layer

FIFO First In First Out
HMI Human-Machine Interface
ID Identifier
IDL Interface Definition Language

IEC International Electrotechnical Commission

Ind Indication
IP Internet Protocol
ISO International Organization for Standardization

LDev Logical Device
LME Layer Management Entity
OSI Open Systems Interconnect
PDev Physical Device
PDU Protocol Data Unit
PL Physical Layer
QoS Quality of Service
REP Route Endpoint
Req Request
Rsp Response
RT Runtime
SAP Service Access Point
SCL Security Level
SDU Service Data Unit
SEM State event matrix
SMIB System Management Information Base
SMK System Management Kernel
STD State transition diagram, used to describe object behaviour
VAO Variable Object
3.8 Conventions
3.8.1 Overview
The FAL is defined as a set of object-oriented ASEs. Each ASE is specified in a separate

subclause. Each ASE specification is composed of two parts, its class specification, and its
service specification.
The class specification defines the attributes of the class. The attributes are accessible from
instances of the class using the Object Management ASE services specified in Clause 5 of
this standard. The service specification defines the services that are provided by the ASE.
3.8.2 General conventions
This standard uses the descriptive conventions given in ISO/IEC 10731.
3.8.3 Conventions for class definitions
Class definitions are described using templates. Each template consists of a list of attributes
for the class. The general form of the template is shown below:

– 18 – IEC 61158-5-4:2014 © IEC 2014

FAL ASE: ASE Name
CLASS: Class Name
CLASS ID: #
PARENT CLASS: Parent Class Name

ATTRIBUTES:
1 (o) Key Attribute: numeric identifier

2 (o) Key Attribute: name
3 (m) Attribute: attribute name(values)

4 (m) Attribute: attribute name(values)

4.1 (s) Attribute: attribute name(values)

4.2 (s) Attribute: attribute name(values)
4.3 (s) Attribute: attribute name(values)
5. (c) Constraint: constraint expression
5.1 (m) Attribute: attribute name(values)
5.2 (o) Attribute: attribute name(values)
6 (m) Attribute: attribute name(values)
6.1 (s) Attribute: attribute name(values)
6.2 (s) Attribute: attribute name(values)
SERVICES:
1 (o) OpsService: service name
2. (c) Constraint: constraint expression
2.1 (o) OpsService: service name
3 (m) MgtService: service name
(1) The "FAL ASE:" entry is the name of the FAL ASE that provides the services for the class
being specified.
(2) The "CLASS:" entry is the name of the class being specified. All objects defined using
this template will be an instance of this class. The class may be specified by this
standard, or by a user of this standard.
(3) The "CLASS ID:" entry is a number that identifies the class being specified. This number
is unique within the FAL ASE that will provide the services for this class. When qualified
by the identity of its FA
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