ISO/IEC 21823-4:2022

Internet of things (IoT) — Interoperability for IoT systems — Part 4: Syntactic interoperability

ISO/IEC 21823-4:2022 specifies the IoT interoperability from a syntactic point of view. In ISO/IEC 21823-1: Framework [2], five facets are described for IoT interoperability, i.e. transport, semantic, syntactic, behavioural and policy. In this document, the following specifications for IoT interoperability from syntactic viewpoint are included; – A principle of how to achieve syntactic interoperability among IoT systems which include IoT devices – Requirements on information related to IoT devices for syntactic interoperability – A framework for processes on developing information exchange rules related to IoT devices from the syntactic viewpoint

Titre manque — Partie 4: Titre manque

General Information

• Status: Published
• Publication Date: 10-Mar-2022
• ICS: 35.020 - Information technology (IT) in general
• Technical Committee: ISO/IEC JTC 1/SC 41 - Internet of things and digital twin
• Drafting Committee: ISO/IEC JTC 1/SC 41 - Internet of things and digital twin
• Current Stage: 6060 - International Standard published
• Start Date: 11-Mar-2022
• Due Date: 09-Sep-2023
• Completion Date: 11-Mar-2022

Standards Content (Sample)

ISO/IEC 21823-4
Edition 1.0 2022-03
INTERNATIONAL
STANDARD
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Internet of things (IoT) – Interoperability for IoT systems –
Part 4: Syntactic interoperability

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ISO/IEC 21823-4
Edition 1.0 2022-03
INTERNATIONAL
STANDARD
colour
inside
Internet of things (IoT) – Interoperability for IoT systems –

Part 4: Syntactic interoperability

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 33.020 ISBN 978-2-8322-1083-4

– 2 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
CONTENTS
FOREWORD . 4
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Abbreviated terms . 7
5 Principle for IoT syntactic interoperability . 7
5.1 General . 7
5.2 Principle for IoT syntactic interoperability . 7
5.3 Relevant technologies for syntactic interoperability . 8
5.3.1 Metamodel and syntactic interoperability . 8
5.3.2 Metamodel-driven approaches supporting interoperability issues . 9
5.4 The overall structure of the proposed approach . 9
5.5 The methodology of metamodel-driven information exchange . 10
5.6 Information exchange rules . 11
5.6.1 Categories of information exchange rules . 11
5.6.2 Information exchange rules expression . 12
5.6.3 Information exchange rules expression example . 12
6 Requirements on information related to IoT devices . 12
6.1 General . 12
6.2 General requirements on the translation rules . 13
6.2.1 General . 13
6.2.2 Required intrinsic properties of physical IoT devices (IPIoT) . 13
6.2.3 Required extrinsic properties of physical IoT devices (EPIoT) . 14
6.3 General requirements on the operation rules . 15
6.3.1 Overview of mismatches between IoT systems . 15
6.3.2 Required properties and syntactic resolutions for potential IoT
mismatches . 17
6.3.3 Details of required properties and syntactic resolutions for potential IoT
mismatches . 18
7 A framework for IoT syntactic interoperability . 30
7.1 General . 30
7.2 A conceptual model for dataset of operation rules (DOR) . 31
7.3 Detailed procedures for a syntactic interoperability framework . 31
7.3.1 Procedure A to prepare the required properties and resolutions . 31
7.3.2 Procedure B to create information exchange rules (DIER) . 32
7.3.3 Procedure C to execute the information exchange rules and check the
result . 32
Annex A (informative) Properties for physical IoT devices and data . 33
A.1 Intrinsic properties of physical IoT devices . 33
A.2 Extrinsic properties of physical IoT devices . 35
Annex B (informative) A use case . 37
B.1 General . 37
B.2 The use case overview: Connected car and vehicle in smart city . 37
B.3 A scenario of this use case . 38
B.3.1 The architecture of this use case . 38

B.3.2 Scenario: Data exchange between a connected car and a traffic
management system (TMS) . 38
B.4 Examples used in this use case . 39
B.4.1 General . 39
B.4.2 Illustrated example files and their relationships . 40
Annex C (informative) Other metamodel definitions . 41
Bibliography . 42

Figure 1 – The overall structure of the proposed approach . 9
Figure 2 – Model hierarchies and metamodel-driven information exchange rules . 10
Figure 3 – Categories of information exchange rules . 11
Figure 4 – Excerpted information exchange rules for Annex B . 12
Figure 5 – Classifications of requirements on information related to IoT devices . 13
Figure 6 – A procedure for mismatch detection and resolution . 16
Figure 7 – An example of mismatch detection and resolution . 17
Figure 8 – A framework for processes on developing information exchange rules
related to IoT devices from the syntactic viewpoint . 30
Figure 9 – An excerpted conceptual model of DOR (dataset of operation rules) . 31
Figure 10 – Steps of Procedure A . 32
Figure B.1 – Overall view of use case 1 . 37
Figure B.2 – Architecture of connected car and vehicle in smart city use case . 38
Figure B.3 – Information exchange between a car and a TMS . 38
Figure B.4 – Relationships of example files for this use case . 40

Table 1 – Required intrinsic properties of physical IoT devices . 14
Table 2 – Required extrinsic properties of physical IoT devices . 15
Table 3 – Required properties and resolutions for potential IoT mismatches . 18
Table 4 – Mismatch1: Synchronization mismatch . 19
Table 5 – Mismatch2: Sampling frequency mismatch . 20
Table 6 – Mismatch3: Location mismatch . 21
Table 7 – Mismatch4: Data recording pattern mismatch . 22
Table 8 – Mismatch5: Precision mismatch. 23
Table 9 – Mismatch6: Significant figure mismatch . 24
Table 10 – Mismatch7:Range mismatch . 25
Table 11 – Mismatch8: Calibration mismatch . 26
Table 12 – Mismatch9: Response time mismatch . 27
Table 13 – Mismatch10: Acquisition status mismatch . 28
Table 14 – Mismatch11: Unit mismatch . 29
Table A.1 – Intrinsic properties of physical IoT devices . 33
Table A.2 – Extrinsic properties of physical IoT devices . 36
Table C.1 – Definitions of metamodel in various resources . 41

– 4 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
INTERNET OF THINGS (IoT) –
INTEROPERABILITY FOR IoT SYSTEMS –

Part 4: Syntactic interoperability

FOREWORD
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ISO/IEC 21823-4 has been prepared by subcommittee 41: Internet of Things and Digital Twin,
of ISO/IEC joint technical committee 1: Information technology. It is an International Standard.
The text of this International Standard is based on the following documents:
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JTC1-SC41/255/FDIS JTC1-SC41/269/RVD
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INTRODUCTION
In the world of the Internet of Things (IoT), heterogeneous systems and devices need to be
connected and exchange data with others. How data exchange can be implemented becomes
a key issue of interoperability among IoT industries. Information models (IMs), which can well
represent specifications of data, are adopted and utilized to solve the interoperability problem.
Meanwhile, as systems and devices in IoT can have different information models with different
modelling methodologies and formats, interoperability based on different information models is
recognized as an urgent problem. The IoT interoperability related systems and applications
have an 11 trillion market potentially [1] .
The ISO/IEC 21823 series standards address issues that relate to interoperability both between
different IoT systems and within a single IoT system. ISO/IEC 21823-1 [2] describes a general
framework for interoperability for IoT systems. It includes a five facet model for interoperability
that includes transport, syntactic, semantic, behavioural, and policy viewpoints.
Different parts of ISO/IEC 21823, based on one of the facets, provide specifications from their
corresponding viewpoints. Each of the parts can refer to others but is independent. Currently,
ISO/IEC 21823-2 [3] defines specifications from the transport viewpoint, ISO/IEC 21823-3 [4]
defines requirements, provides guidance, etc. from the semantic viewpoint, and
ISO/IEC 21823-4 specifies the syntactic interoperability.
Syntactic interoperability means that exchanged information can be understood by the
participating IoT systems which contain IoT devices. In more detail, the syntactic interoperability
is related to the information models' representing formats, structures, and grammar of their
modelling languages such as a length of a data string, constraints on data types, and forbidden
characters.
This document first provides the principle of how to achieve syntactic interoperability based on
metamodel-driven approaches. In other words, the reason why the information exchange rules
based on metamodels can support syntactic interoperability among different IoT systems will
be elaborated. Secondly, requirements on information models such as metamodels and models
of IoT systems including IoT devices are described. Features related to IoT devices such as the
identifier, device type, setup environments, and functions need to be considered to accomplish
syntactic interoperability among different information models utilized in IoT systems. Thirdly, a
framework for processes on developing information exchange rules related to IoT devices from
the syntactic viewpoint is provided. For example, the kinds of metamodels, and the types of
entities and relationships that shall be selected are specified, and the procedure of how to build
the information exchange rules from different information models is provided.
In Annex A, possible intrinsic and extrinsic properties of IoT devices are listed as additional
information of Clause 6. In Annex B, a use case of how the syntactic interoperability in
accordance with specifications in this document among industrial IoT systems and IoT devices
is described.
With this document, system and device vendors, who need to improve and/or develop their
products to comply with IoT requirements, can implement specifications of this document to
their products for an automatic or semi-automatic realization of IoT syntactic interoperability.

_____________
Numbers in square brackets refer to the Bibliography.

– 6 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
INTERNET OF THINGS (IoT) –
INTEROPERABILITY FOR IoT SYSTEMS –

Part 4: Syntactic interoperability

1 Scope
This part of ISO/IEC 21823 specifies the IoT interoperability from a syntactic point of view. In
this document, the following specifications for IoT interoperability from a syntactic viewpoint are
included:
– a principle of how to achieve syntactic interoperability among IoT systems which include IoT
devices;
– requirements on information related to IoT devices for syntactic interoperability;
– a framework for processes on developing information exchange rules related to IoT devices
from the syntactic viewpoint.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
ISO/IEC 20924, Internet of Things (IoT) – Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 20924 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following web
addresses:
• ISO Online browsing platform: available at http://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1
instance
individual entity having its own value and possibly its own identity
[SOURCE: ISO 19103:2015 [5], 4.20]
3.2
metamodel
special kind of model that specifies the abstract syntax of a modelling language
Note 1 to entry: A model is an instance (3.1) of a metamodel
Note 2 to entry: IoT syntactic interoperability is achieved by information exchange rules through the structure, data
format, and syntactic constraints using syntactic aspects of the metamodel.

[SOURCE: ISO/IEC 19506:2012 [6], modified – The description that follows the definition has
been deleted. Notes to entry have been added.]
3.3
model
abstraction of some aspects of reality
[SOURCE: ISO 19109:2015 [7], 4.15]
3.4
property
particular characteristic of an object type
[SOURCE: ISO 16484-5:2017 [8], 3.2.74]
3.5
syntactic interoperability
interoperability such that the formats of the exchanged information can be understood by the
participating systems
Note 1 to entry: System means IoT system.
Note 2 to entry: IoT device, IoT gateway, sensor and actuator are considered as system.
[SOURCE: ISO/IEC 19941:2017 [9], 3.1.4, modified – Notes to entry have been added.]
4 Abbreviated terms
CRS coordinate reference system
EPIoT extrinsic properties of physical IoT devices
IPIoT intrinsic properties of physical IoT devices
IoT Internet of Things
JSON JavaScript Object Notation
MOF Meta Object Facility
UML Unified Modelling Language
XML extensible markup language
5 Principle for IoT syntactic interoperability
5.1 General
In the ISO/IEC 21823 series, ISO/IEC 21823-1 [2] defines an overall framework for IoT
interoperability. It specifies that IoT interoperability shall be supported by standards from five
facets: transport, semantic, syntactic, behavioural, and policy. A standard based on each of the
facets shall provide specifications from its corresponding viewpoint. Each of the standards can
refer to or can be independent of standards based on other facets. ISO/IEC 21823-2 [3] defines
specifications from the transport viewpoint. ISO/IEC 21823‑3 [4] defines requirements, provides
guidance, etc. from the semantic aspect. ISO/IEC 21823-4 (this document) addresses the
syntactic interoperability that provides specifications from the syntax viewpoint.
5.2 Principle for IoT syntactic interoperability
In this subclause, a principle for IoT syntactic interoperability is specified. In order for an IoT
system to achieve syntactic interoperability with other IoT systems and devices, the information
exchange rules between their data are adopted.

– 8 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
The information exchange rules for syntactic interoperability provide the following types of
information exchange.
a) Format exchange.
– The term "format" is bound for a data format.
– The "format exchange" means that information in different data formats can be
exchanged.
For example, data in the UML format can be exchanged with data in the XML format.
b) Structure exchange.
– The term "structure" is bound for a data structure that has a hierarchy and branches.
– The "structure exchange" means that information in different structures can be
exchanged.
For example, information defined in a hierarchical tree structure can be transformed into a
flat tree structure.
c) Syntactic constraint exchange.
– The term "constraint" is a condition related to syntax or syntactic requirements on data.
– The "syntactic constraint exchange" means that information with different constraints
can be exchanged.
For example, data in IoT System1 have a value of one digit after the decimal point, and data
in IoT System2 have a value of two digits after the decimal point. Their data accuracy
exchange is classified into syntactic constraint exchange.
Furthermore, information of IoT systems is expressed with models. In each IoT system, its
information can be represented with a metamodel, models, and instances [10]. In order to
describe information exchange rules between IoT systems for their syntactic interoperability,
syntactic aspects in their metamodels and models are utilized. In addition, specific requirements
for metamodels, models, and information exchanges in the IoT domain are included in this
document.
5.3 Relevant technologies for syntactic interoperability
5.3.1 Metamodel and syntactic interoperability
A metamodel, as the model's model, consists of statements about models. Especially in the
UML as described in [10], the metamodel specifies the abstract syntax of the UML. The abstract
syntax defines the set of UML modelling concepts, attributes, relationships as well as rules for
combining concepts to construct partial UML models.
There are also other definitions for metamodel in ISO/IEC and IEEE standards. Some of them
are listed in Table C.1 in Annex C. Several metamodel definitions in different resources are
collected in ISO/IEC/IEEE 24765:2017 [11]. In this document, Definition 7 of metamodel in
Table C.1, i.e. "special kind of model that specifies the abstract syntax of a modelling language",
is adopted. From this definition, it is clear that an approach of creating information exchange
rules with elements available in metamodels is actually based on the syntax and therefore is
acceptable for syntactical interoperability. UML, OWL (Ontology Language), OntoML (Ontology
[12]), XML, etc. are modelling languages adopted and utilized in different
Markup Language
systems and domains.
5.3.2 Metamodel-driven approaches supporting interoperability issues
Metamodel-driven information exchange and interoperability approaches are adopted as
holistic approaches in industry domains [13], [14] to enable a model-driven engineering
approach in the area of information integration and interoperation. By creating declarative
mapping specifications, i.e. exchange rules, automatic information exchange can be executed
at run-time and off-line among heterogeneous systems and devices. As the metamodel-driven
approaches tackle the interoperability problems at a higher abstraction level than models, it can
increase the efficiency of achieving interoperability among heterogeneous systems and devices
which comply with the same metamodel. In other words, information exchange rules can be
reused by IoT systems and IoT devices whose information models are in compliance with the
same metamodel.
5.4 The overall structure of the proposed approach

Figure 1 – The overall structure of the proposed approach
Figure 1 illustrates the overall structure of the proposed approach. Figure 1 shows two IoT
systems: IoT System1 and IoT System2. In each IoT system, its information consists of a
metamodel, model, and instance data. In order to achieve syntactic interoperability between
these two systems, the information exchange rules based on the metamodels of both IoT
systems need to be created. To create information exchange rules, their required properties
and resolutions to support executing information exchange need to be analysed and defined.
In Figure 1:
– lines starting with "#" denote comment lines;
– in the text box of "information exchange rule example", sample information for syntactic
interoperability is listed;
– in the text box of "required properties and resolutions", example properties and syntactic
resolution for mismatch are listed.
In this document, three major clauses are specified to support achieving IoT syntactic
interoperability.
– 10 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
a) In Clause 5, relevant technologies of the metamodel and their applicability in the area of
solving syntactical interoperability issues are explained. The methodology of how to create
information exchange rules among heterogeneous IoT systems and devices is specified.
The information exchange rules are in general categorized into two groups:
1) translation rules that specify transformations among elements in metamodels. Details
are in 5.6;
2) operation rules that specify mismatches between IoT systems. Details are in 6.3.
b) In Clause 6, requirements on IoT-related information are specified. Requirements include:
1) firstly, the required properties related to IoT devices for translation rules (specified in
6.2). For example, an identifier of an IoT system or an IoT device is a required property;
2) secondly, the required properties and resolutions for mismatches between IoT systems
for operation rules. Mismatches occur during information exchange between IoT
systems. Resolutions are required to resolve these mismatches. For example, if the time
interval requesting information exchange is different, i.e. not matched in involved IoT
systems for their interoperability, then syntactic resolutions are required to fill up this
mismatch. Required properties and resolutions for mismatches are analysed and
described in 6.3.
c) In Clause 7, a framework of how to create information exchange rules is specified. The
necessary procedures to realize the IoT syntactic interoperability following the proposed
approach are defined. Whether it is necessary to create or extend an IoT system's
metamodel, what kinds of information exchange rules are defined, and how exchange rules
can be executed and evaluated are also described.
5.5 The methodology of metamodel-driven information exchange

Figure 2 – Model hierarchies and metamodel-driven information exchange rules
During the last decades, in the field of model-based engineering (MBE), models have been
constructed to represent information from the physical world. The community of OMG proposes
MOF (ISO/IEC 19502 [15]), a four-layer modelling architecture to describe models. Models here
in general include the instance in M0-Layer, the model in M1-Layer, the metamodel in M2-Layer,
and the meta-metamodel in M3-Layer. M3-Layer is not included in this document thus it is
omitted from Figure 2.
As shown in Figure 2, the model in M1-Layer defines structures, available entities, relationships,
etc. for instances in M0-Layer, and the metamodel in M2-Layer specifies the syntax for the
models. Therefore, models in M1-Layer are the instances of their metamodel in M2-Layer, i.e.
M1-Layer has relationships with M2-Layer as "<>". And the same relationships
exist between M0-Layer and M1-Layer. Each metamodel can have many models and each
model can have many instances. In Figure 2, Model1 in IoT System1 is the model of Instance1,
and Metamodel1 is the metamodel of Model1. Model2 and Metamodel2 in IoT System2 have
the same relationships.
From the syntactic point of view, information exchange rules as projections allow converting
information in all layers from a specific system to information in another system in a modelling
environment. The information exchange rules based on metamodels in M2-Layer are applicable
because the information in M1-Layer is
to the transformation of models in M1-Layer [15][16]
defined with elements available in M2-Layer. The same relationships are applicable to M1-Layer
and M0-Layer. Therefore, the metamodel-based information exchange rules are applicable to
its models and instances.
5.6 Information exchange rules
5.6.1 Categories of information exchange rules
As explained in 5.2 and 5.5, for an IoT system including IoT devices (IoT System1), in order to
achieve syntactic interoperability with other IoT systems and devices (IoT System2), information
exchange rules are adopted. Figure 3 shows that the information exchange rules can be
classified into two categories.
– Translation rules
Translation rules are created with elements in the metamodels of IoT System1 and IoT
System2. Elements in the metamodels are classes, properties, relationships, etc.
Transformation rules among these elements are defined and named "translation rules" in
order to achieve structure, data format, and syntactic constraints transformations between
IoT systems. Required properties for translation rules are specified in 6.2.
– Operation rules
Operation rules are specified to resolve mismatches between two IoT systems. Potential
operational mismatches that happen during processes of achieving interoperability are
detected. To solve these mismatches, necessary properties and available resolutions are
specified. Mismatches that cannot be resolved from syntactic viewpoints are out of the
scope. Simultaneously, resolutions not based on syntactic approaches for mismatches are
also out of the scope. Details of the operation rules are specified in 6.3.

The overlapped area includes properties used both in translation rules and operation rules.
Figure 3 – Categories of information exchange rules

– 12 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
5.6.2 Information exchange rules expression
Information exchange rules shall include translation rules among metamodels, and operation
rules for IoT syntactic interoperability. Information exchange rules can be expressed in various
languages. Some well-known languages such as QVT (Query/View/Transformation [17]),
OCL (Object Constraint Language [18]), ATL (Atlas Transformation Language [19]),
TGG (Triple graph grammar [20], [21]), etc. can be applied to describe information exchange
rules among different metamodels and models. This document does not provide new languages
for information exchange rules, and sample information exchange rules are described in
Annex B. An implementation of this document can define information exchange rules with
selected language and data format.
5.6.3 Information exchange rules expression example

Figure 4 – Excerpted information exchange rules for Annex B
Excerpted information exchange rules in ATL for Annex B are listed in Figure 4. In Figure 4;
– IoT System1 is a connected vehicle; IoT System2 is a traffic management system (TMS)
adopting FIWARE to represent its system. Metamodels of these two systems are defined in
line (2) as IN: ProbeVehicle and OUT: Fiware, respectively.
– Lines (4) to (12) show the translation rule of a vehicle "name" and "identifier" to the TMS
"name". Properties utilized in translation rules are defined separately in each metamodel
[22] and [23].
– Lines (15) and (16) show an implementation of the operation rule for a unit mismatch
resolution. Here, while the unit mismatch is detected, the exchange between different units
is specified manually. As explained in 6.3, the implementations of resolutions are out of the
scope. This example is a guide for implementers.
6 Requirements on information related to IoT devices
6.1 General
In Clause 6, requirements on the information which is necessary for IoT syntactic
interoperability are described. The information shall be defined in the metamodel or model of
an IoT system or an IoT device. The requirements apply to IoT devices for the data exchange
among IoT systems, excluding cloud-computing-based back-end services.
In coincidence with the two categories of the information exchange rues described in 5.6.1, the
requirements for the information related to IoT devices are also classified into two groups: the
requirements on translation rules and those on operation rules as shown in Figure 5.

– Requirements on translation rules are further divided into two groups depending on required
properties. One group is "Required intrinsic properties of physical IoT devices" and the other
is "Required extrinsic properties of physical IoT devices" [24], [25]. They are specified in
6.2.2 and 6.2.3, respectively. An intrinsic property is defined as a property of a specified
subject that exists itself or within the subject, and an extrinsic property is a property not
essential or inherent to the subject that is being characterized [25].
– Required properties and resolutions for operation rules are specified in 6.3.

Figure 5 – Classifications of requirements on information related to IoT devices
6.2 General requirements on the translation rules
6.2.1 General
The translation rules are specified with elements in metamodels of IoT systems. An IoT system
contains IoT devices, and the information of IoT devices is represented with properties. In 6.2,
required properties related to IoT devices for syntactic interoperability are specified.
– No new identification structure nor new data modelling method is specified in this document
for IoT syntactic interoperability.
– Existing ID standards and data models adopted in the IoT systems shall be applied if they
are used in an IoT system while realizing its syntactic interoperability.
– For each property, no specific property definitions, formats, or classifications are required.
But if there are standards for its definition, format, etc., and these standards are used in an
IoT system, then the property complying with these standards shall be applied for realizing
its IoT syntactic interoperability.
NOTE The above descriptions are to avoid misunderstanding.
6.2.2 Required intrinsic properties of physical IoT devices (IPIoT)
In order to support IoT syntactic interoperability, intrinsic properties of physical IoT devices are
required and provided by an IoT system. Available informative intrinsic properties are listed in
Clause A.1. Some typical properties utilized in IoT use cases are explained in Table 1.

– 14 – ISO/IEC 21823-4:2022 © ISO/IEC 2022
Table 1 – Required intrinsic properties of physical IoT devices
Property name Description Mandatory/Optional
ID IoT device identifier based on a given Mandatory
standardized object identification system.
Name IoT device name. Optional
NOTE For example, UID, IRDI,
identifiable string name such as
"DevicID.temperature" can be used.
DeviceType Type of an IoT device. It shall be a Mandatory
sensor, actuator, composed IoT device,
NOTE Value of this property can be
and any user-defined device type.
null.
Location Uniquely identifiable physical point or Optional
area
Note 1 to entry: The location can be
characterized by coordinates.
[SOURCE: ISO 29404:2015, 3.11]
NOTE For a moveable IoT device, the
current coordinates obtained from a
positioning system such as GPS can be
used as the location. For a fixed IoT
device its setting location can be utilized.
DeviceOwner Person(s) or organization(s) which has Optional
legal title to the product to be used
Note 1 to entry: The owner may also be
the operator.
[SOURCE: ISO/TR 20183:2015, 2.21]
MaintenanceRecord Device maintenance history Optional

6.2.3 Required extrinsic properties of physical IoT devices (EPIoT)
In order to support IoT syntactic interoperability, extrinsic properties of physical IoT devices are
required and provided by an IoT system. Extrinsic properties shall be defined in a
metamodel/model of an IoT device or an IoT system. Available informative extrinsic properties
are listed in Clause A.2. Some typical properties utilized in IoT use cases are explained in
Table 2.
Table 2 – Required extrinsic properties of physical IoT devices
Property name Description Mandatory
/Optional
DataID Identifier of a piece of data based on a given standardized Mandatory
or user-defined data reference system.
DeviceID ID of the device from which a datum is collected. Mandatory
NOTE "ID" in Table 1 shall be used.
Value Data value Mandatory
[SOURCE: ISO/IEC 20944-1:2013, 3.18.2.7]
Timestamp Attribute or field in data which denotes the time of data Mandatory
generation
[SOURCE: ISO/TS 27790:2009, 3.73]
Accuracy Closeness of agreement between a test result or Optional
measurement result and the true value.
[SOURCE: ISO 3534-2:2006, 3.3.1]
AccessAuthority Access permission such as forbidden, readable, writable, Optional
executable to device datum.
NOTE Device data means data produced by the device in
operation.
6.3 General requirements on the operation rules
6.3.1 Overview of mismatches between IoT systems
Required properties and resolutions for operation rules are related to the mismatches between
what one IoT system is expecting and what the other IoT system can provide. A mismatch is a
difference between these two IoT systems regarding a specified property for data. To
accomplish syntactic interoperability, the mismatches between IoT systems are detected by
comparing the required properties of two IoT systems. The operation rules are prepared to
resolve the mismatches. These required properties and resolutions are defined as requirements
on the operation rules.
Figure 6 shows the overall procedures for mismatch detection and resolution. Firstly, the
mismatch is detected by comparing the required properties. If the property is defined in the
metamodel, the translation rule is created to resolve the format and structural differences. After
creating the translation rules, the operation rules are created. If the property is not defined in
the metamodel, either the metamodel is extended to include the property, or operation rules are
directly created.
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Figure 6 – A procedure for mismatch detection and resolution
Figure 7 shows an example of IoT mismatch and its syntactic resolution. IoT System2 requires
data with 3 significant figures for the temperature, while IoT System1 can provide data with 5
significant figures. Required properties for this mismatch are "significantFigure". The
"significantFigure" describes the precision or uncertainty of data by the number of digits. The
property of IoT System1 has RDF format, while the property of IoT System2 has JSON format,
thus they have format differences. They also have structural differences.
In the example in Figure 7, firstly, the mismatch is detected by comparing the "significantFigure"
properties. Then, the differences in format and structure are resolved by translation rules. For
example, IoT System
...