SIST EN ISO 19118:2011

SLOVENSKI STANDARD
01-december-2011
1DGRPHãþD
SIST EN ISO 19118:2006
Geografske informacije - Kodiranje (ISO 19118:2011)
Geographic information - Encoding (ISO 19118:2011)
Geoinformation - Kodierung (ISO 19118:2011)
Information géographique - Codage (ISO 19118:2011)
Ta slovenski standard je istoveten z: EN ISO 19118:2011
ICS:
07.040 Astronomija. Geodezija. Astronomy. Geodesy.
Geografija Geography
35.240.70 Uporabniške rešitve IT v IT applications in science
znanosti
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 19118
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2011
ICS 35.240.70 Supersedes EN ISO 19118:2006
English Version
Geographic information - Encoding (ISO 19118:2011)
Information géographique - Codage (ISO 19118:2011) Geoinformation - Kodierung (ISO 19118:2011)
This European Standard was approved by CEN on 1 October 2011.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 19118:2011: E
worldwide for CEN national Members.

Contents Page
Foreword .3
Foreword
This document (EN ISO 19118:2011) has been prepared by Technical Committee ISO/TC 211 "Geographic
information/Geomatics" in collaboration with Technical Committee CEN/TC 287 “Geographic Information” the
secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by April 2012, and conflicting national standards shall be withdrawn at the
latest by April 2012.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 19118:2006.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 19118:2011 has been approved by CEN as a EN ISO 19118:2011 without any modification.

INTERNATIONAL ISO
STANDARD 19118
Second edition
2011-10-15
Geographic information — Encoding
Information géographique — Codage

Reference number
ISO 19118:2011(E)
©
ISO 2011
ISO 19118:2011(E)
©  ISO 2011
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO 2011 – All rights reserved

ISO 19118:2011(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Conformance . 1
2.1  Introduction . 1
2.2  Conformance classes related to encoding rules . 1
2.3  Conformance classes related to encoding services . 1
3  Normative references . 2
4  Terms and definitions . 2
5  Symbols and abbreviated terms . 6
6  Fundamental concepts and assumptions . 7
6.1  Concepts . 7
6.2  Data interchange . 7
6.3  Application schema . 8
6.4  Encoding rule . 9
6.5  Encoding service . 10
6.6  Transfer service . 10
7  Character repertoire . 11
8  Generic instance model . 11
8.1  Introduction . 11
8.2  Relation between UML and the instance model . 14
9  Encoding rules . 14
9.1  Introduction . 14
9.2  General encoding requirements . 15
9.3  Input data structure . 17
9.4  Output data structure . 17
9.5  Conversion rules . 18
9.6  Examples . 18
10  Encoding service . 18
Annex A (normative) XML-based encoding rule . 20
Annex B (normative) Abstract test suit . 21
Annex C (informative) XML-based encoding rule in use by communities . 25
Bibliography . 68

ISO 19118:2011(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 19118 was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics.
This second edition cancels and replaces the first edition (ISO 19118:2005), which has been technically
revised.
iv © ISO 2011 – All rights reserved

ISO 19118:2011(E)
Introduction
This International Standard specifies the requirements for defining encoding rules used for interchange of
geographic data within the set of International Standards known as the “ISO 19100 series”. An encoding rule
allows geographic information defined by application schemas and standardized schemas to be coded into a
system-independent data structure suitable for transport and storage. The encoding rule specifies the types of
data being coded and the syntax, structure and coding schemes used in the resulting data structure. The
resulting data structure can be stored on digital media or transferred using transfer protocols. It is intended
that the data be read and interpreted by computers, but data can be in a form that is human readable.
The choice of one encoding rule for application-independent data interchange does not exclude application
domains and individual nations from defining and using their own encoding rules that can be platform
dependent or more effective with regard to data size or processing complexity. XML is a subset of
ISO/IEC 8879 and has been chosen because it is independent of computing platform and interoperable with
the World Wide Web.
This International Standard is divided into three logical sections. The requirements for creating encoding rules
based on UML schemas are specified in Clauses 6 to 9. The requirements for creating encoding service are
specified in Clause 10, and the requirements for XML-based encoding rules are specified in Annex A.
The XML-based encoding rule is intended for use as a neutral data interchange. It relies on the Extensible
Markup Language (XML) and the ISO/IEC 10646 character set standards.
The geographic information standards are organized within the set of International Standards known as the
“ISO 19100 series”. The background and the overall structure of this series of International Standards and the
fundamental description techniques are defined in ISO 19101, ISO/TS 19103 and ISO/TS 19104.
Users of this International Standard can develop application schemas to formally describe geographic
information. An application schema is compiled by integrating elements from other standardized conceptual
schemas (e.g. ISO 19107). How this integration takes place is described in ISO 19109. The set of
International Standards known as the “ISO 19100 series” also defines a set of common services that are
available when developing geographic information applications. The common services are generally defined in
ISO 19119 and cover access to, and processing of, geographic information according to the common
information model. This International Standard covers implementation issues.

INTERNATIONAL STANDARD ISO 19118:2011(E)

Geographic information — Encoding
1 Scope
This International Standard specifies the requirements for defining encoding rules for use for the interchange
of data that conform to the geographic information in the set of International Standards known as the
“ISO 19100 series”.
This International Standard specifies
 requirements for creating encoding rules based on UML schemas,
 requirements for creating encoding services, and
 requirements for XML-based encoding rules for neutral interchange of data.
This International Standard does not specify any digital media, does not define any transfer services or
transfer protocols, nor does it specify how to encode inline large images.
2 Conformance
2.1 Introduction
Two sets of conformance classes are defined for this International Standard.
2.2 Conformance classes related to encoding rules
All encoding rules shall pass all test cases of the abstract test suite in B.1. All encoding rules shall pass all test
cases of the abstract test suite in B.2 and/or B.3.
Table 1 — Conformance classes related to encoding rules
Subclause of the
Conformance class
abstract test suite
All encoding rules B.1
Encoding rule with instance conversion B.2
Encoding rule with schema conversion B.3

2.3 Conformance classes related to encoding services
All encoding services shall pass all test cases of the abstract test suite in B.4. Depending on the capabilities of
the encoding service, it shall pass all test cases of additional conformance classes in accordance with Table 2.
ISO 19118:2011(E)
Table 2 — Conformance classes related to encoding services
Subclause of the
Conformance class
abstract test suite
All encoding services B.4
Generic encoding service B.5
Service that encodes data B.6
Service that decodes data B.7
Service that generates an output data structure schema B.8

3 Normative references
The following referenced documents are indispensable for the application 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 8601:2004, Data elements and interchange formats — Information interchange — Representation of
dates and times
ISO/IEC 10646:2011, Information technology — Universal Coded Character Set (UCS)
ISO/TS 19103:2005, Geographic information — Conceptual schema language
ISO 19109:2005, Geographic information — Rules for application schema
Extensible Markup Language (XML) 1.0, W3C Recommendation. Available at

4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1
application schema
conceptual schema (4.5) for data (4.8) required by one or more applications
[ISO 19101:2002, 4.2]
NOTE An application schema describes the content, the structure and the constraints applicable to information
(4.22) in a specific application domain.
4.2
character
member of a set of elements that is used for the representation, organization, or control of data (4.8)
[ISO/IEC 2382-1:1993, 01.02.11]
4.3
code
representation of a label according to a specified scheme
2 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
4.4
conceptual model
model (4.27) that defines concepts of a universe of discourse (4.33)
[ISO 19101:2002, 4.4]
4.5
conceptual schema
formal description of a conceptual model (4.4)
[ISO 19101:2002, 4.5]
4.6
conceptual schema language
formal language based on a conceptual formalism for the purpose of representing conceptual schemas (4.5)
[ISO 19101:2002, 4.6]
EXAMPLES UML, EXPRESS, IDEF1X.
NOTE A conceptual schema language may be lexical or graphical.
4.7
conversion rule
rule for converting instances in the input data (4.8) structure to instances in the output data structure
4.8
data
reinterpretable representation of information (4.22) in a formalized manner suitable for communication,
interpretation, or processing
[ISO/IEC 2382-1:1993, 01.01.02]
4.9
data interchange
delivery, receipt and interpretation of data (4.8)
4.10
data transfer
movement of data (4.8) from one point to another over a medium (4.26)
NOTE Transfer of information (4.22) implies transfer of data.
4.11
data type
specification of a value domain (4.34) with operations allowed on values in this domain
[ISO/TS 19103:2005, 4.1.5]
EXAMPLES Integer, Real, Boolean, String and Date.
NOTE A data type is identified by a term, e.g. Integer. Values of the data types are of the specified value domain, e.g.
all integer numbers between –65537 and 65536. The set of operations can be +, -, * and / and is semantically well defined.
A data type can be simple or complex. A simple data type defines a value domain where values are considered atomic in
a certain context, e.g. Integer. A complex data type is a collection of data types that are grouped together. A complex data
type may represent an object and can, thus, have identity.
ISO 19118:2011(E)
4.12
dataset
identifiable collection of data (4.8)
[ISO 19115:2003, 4.2]
4.13
encoding
conversion of data (4.8) into a series of codes (4.3)
4.14
encoding rule
identifiable collection of conversion rules (4.7) that define the encoding (4.13) for a particular data (4.8)
structure
EXAMPLES XML, ISO 10303-21, ISO/IEC 8211.
NOTE An encoding rule specifies the types of data being converted as well as the syntax, structure and codes (4.3)
used in the resulting data structure.
4.15
encoding service
software component that has an encoding rule (4.14) implemented
4.16
feature
abstraction of real world phenomena
[ISO 19101:2002, 4.11]
NOTE A feature may occur as a type or an instance. Feature type or feature instance is used when only one is meant.
4.17
file
named set of records stored or processed as a unit
[ISO/IEC 2382-1:1993, 01.08.06]
4.18
geographic data
data (4.8) with implicit or explicit reference to a location relative to the Earth
[ISO 19109:2005, 4.12]
4.19
geographic information
information (4.22) concerning phenomena implicitly or explicitly associated with a location relative to the
Earth
[ISO 19101:2002, 4.16]
4.20
identifier
linguistically independent sequence of characters (4.2) capable of uniquely and permanently identifying that
with which it is associated
[ISO 19135:2005, 4.1.5]
4 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
4.21
identification convention
set of rules for creating identifiers (4.20)
4.22
information
knowledge concerning objects, such as facts, events, things, processes, or ideas, including concepts, that
within a certain context has a particular meaning
[ISO/IEC 2382-1:1993, 01.01.01]
4.23
instance model
representation model (4.27) for storing data (4.8) according to an application schema (4.1)
4.24
interface
UML named set of operations that characterize the behaviour of an element
[ISO/IEC 19501]
4.25
interoperability
capability to communicate, execute programs, or transfer data (4.8) among various functional units in a
manner that requires the user to have little or no knowledge of the unique characteristics of those units
[ISO/IEC 2382-1:1993, 01.01.47]
4.26
medium
substance or agency for storing or transmitting data (4.8)
[1]
EXAMPLES Compact disc, internet , radio waves, etc.
4.27
model
abstraction of some aspects of reality
[ISO 19109:2005, 4.14]
4.28
schema
formal description of a model (4.27)
[ISO 19101:2002, 4.25]
4.29
schema model
representation model (4.27) for storing schemas (4.28)
EXAMPLE Representation model for a schema repository.
4.30
stereotype
UML new type of modelling element that extends the semantics of the metamodel
[ISO/IEC 19501]
ISO 19118:2011(E)
NOTE It is necessary that stereotypes be based on certain existing types or classes in the metamodel. Stereotypes
may extend the semantics, but not the structure, of pre-existing types and classes. Certain stereotypes are predefined in
the UML, others may be user-defined. Stereotypes are one of three extensibility mechanisms in UML; the others are
constraint and tagged value.
4.31
transfer protocol
common set of rules for defining interactions between distributed systems
4.32
transfer unit
collection of data (4.8) for the purpose of a data transfer (4.10)
NOTE A transfer unit does not have to be identifiable like a dataset (4.12).
4.33
universe of discourse
view of the real or hypothetical world that includes everything of interest
[ISO 19101:2002, 4.29]
4.34
value domain
set of accepted values
[ISO/TS 19103:2005, 4.1.15]
EXAMPLE The range 3-28, all integers, any character, enumeration of all accepted values (green, blue, white).
5 Symbols and abbreviated terms
DCE Distributed computing environment
DUID Domain unique identifier
HTML Hypertext markup language
MODIS Moderate resolution imaging spectroradiometer
POSC Petroleum Open Standards Consortium
TIFF Tagged image file format
UCS Universal multiple-octet coded character set
UML Unified modelling language
UTF UCS Transfer format
UUID Universally unique identifier
XML Extensible markup language
6 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
6 Fundamental concepts and assumptions
6.1 Concepts
The purpose of the set of International Standards known as the “ISO 19100 series” is to enable interoperability
between heterogeneous geographic information systems. To achieve interoperability between heterogeneous
systems, it is necessary to determine two fundamental issues. The first issue is to define the semantics of the
content and the logical structures of geographic data. This shall be done in an application schema. The
second issue is to define a system- and platform-independent data structure that can represent data
corresponding to the application schema.
The fundamental concepts of data interchange, i.e. the procedure based on the application schema for
encoding, delivery, receipt and interpretation of geographic data, are described in 6.2 to 6.6. An overview of
the data interchange process is described in 6.2; 6.3 introduces application schemas that allow interpretation
of geographic data; 6.4 describes the importance of the encoding rule for producing system-independent data
structures; 6.5 describes a software component, called the encoding service, for executing the encoding rule;
and 6.6 describes the procedure for delivery and receipt, called the transfer service.
6.2 Data interchange
An overview of a data interchange is shown in Figure 1. System A wants to send a dataset to system B. To
ensure a successful interchange, it is necessary that A and B decide on three things: i.e. a common
application schema I, which encoding rule R to apply, and what kind of transfer protocol to use. The
application schema is the basis of a successful data transfer and defines the possible content and structure of
the transferred data, whereas the encoding rule defines the conversion rules for how to code the data into a
system-independent data structure.
System A System B
Application
schema
Internal Internal
I
schema schema
A B
Internal Internal
i i
M M
A B
AI IB
database database
Encoding
Encoding
service
service
(Decoding)
R
-1
R
d
d
File Transfer Transfer File
system services services system
Defines
Data transfer
Data flow
System boundary System boundary

Figure 1 — Overview of data interchange between two systems
ISO 19118:2011(E)
Both systems, A and B, store data in an internal database according to an internal schema, but the schemas
are usually different, i.e. schema A is not equal to schema B. It is necessary to take the following logical steps
in order to transfer a dataset from A's internal database to B's internal database.
a) The first step for system A is to translate its internal data into a data structure that is in accordance with
the common application schema I. Here, this is done by defining a mapping from the concepts of the
internal schema to the concepts defined in the application schema and by writing appropriate mapping
software to translate the data instances. In Figure 1, this mapping is denoted as M . The result is an
AI
application-schema-specific data structure, i . The data structure is stored in memory or on an
A
intermediate file and is system-dependent and, thus, is not suitable for transfer.
b) The next step is to use an encoding service, which applies the encoding rule R to create a data structure
that is system independent and, therefore, suitable for transfer. This encoded dataset is called d and may
be stored in a file system or transferred using a transfer service.
c) System A then invokes a transfer service to send the encoded dataset d to system B. The transfer service
follows a transfer protocol for how to do packaging and how the actual transportation over an on-line or
off-line communication medium should take place. It is necessary that both parties agree on the transfer
protocol used.
d) The transfer service on system B receives the transferred dataset, and according to the protocol the
dataset is unpacked and stored as an encoded dataset d, e.g. on an intermediate file.
e) In order to get an application-schema-specific data structure i , system B applies the inverse encoding
B
1
rule R to interpret the encoded data.
f) To use the dataset, it is necessary that B translate the application-schema-specific data structure i into
B
its internal database. This is done by defining a mapping from the application schema into its internal
schema and by writing software that does the actual translation. In Figure 1 this mapping is denoted M .
IB
This International Standard specifies only the requirements for creating encoding rules and the encoding
services and not the whole data interchange process. Thus, only steps b) and e) are standardized. Steps a),
c), d) and f) use general information technology services.
6.3 Application schema
An application schema is a conceptual schema for applications with similar data requirements. The application
schema is the basis of a successful data interchange and defines the possible content and structure of the
data. It is also the basis for implementing application-schema-specific data structures for local storage of data.
The application schema used for encoding in compliance with this International Standard shall be written in
the UML conceptual schema language, in accordance with ISO/TS 19103 and ISO 19109. These International
Standards specify a framework for how to write application schemas. The rules include specifications on how
to use standardized schemas to define feature types. It is necessary that both a sender and a receiver of data
have access to the application schema.
The application schema shall be accessible to both ends of a data interchange to ensure a successful result. It
is necessary that the application schema be transferred before data interchange takes place, so that both the
receiver and sender can prepare their systems by implementing mappings and data structures according to
the application schema. It may be transferred together with the dataset, or it may be stored in a public place
and referenced from the dataset.
The application schema may be interchanged by paper- or electronic-based methods.
8 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
6.4 Encoding rule
6.4.1 Concept
An encoding rule is an identifiable collection of conversion rules that defines the encoding for a particular data
structure. The encoding rule specifies the data types being converted, as well as the syntax, structure and
coding schemes used in the resulting data structure. An encoding rule is applied to application-schema-
specific data structures to produce system-independent data structures suitable for transport or storage. In
order to define an encoding rule, it is necessary that three important aspects be specified: the input data
structure, the output data structure and the conversion rules between the elements of the input and the output
data structures. Both the input and output data structures are written using a conceptual schema language
and the concepts in the languages are used to define the encoding rule.
6.4.2 Input data structure
The input data structure is an application-schema-specific data structure. The data structure can be thought of
as a set of data instances, i.e. i  {i , ., i }; see Figure 1. Each data instance, i , is an instance of a concept,
1 p k
I, defined in an application schema. The application schema defines a set of concepts defined in the
l
application schema I  {I , ., I }.
1 m
The application schema is a conceptual schema, c, written in a conceptual schema language, C. The
conceptual schema defines a set of concepts c  {c , ., c } by instantiating the concepts of the conceptual
1 m
schema language C  {C , ., C }. Since the application schema is a conceptual schema, c  I.
1 r
6.4.3 Output data structure
The output data structure is defined by a schema, D  {D , ., D }. D is the schema for the output structure
1 s
and is not shown in Figure 1. The output data structure can be thought of as a set of data instances, i.e.
d  {d , ., d } where each data instance, d , is an instance of a concept, D .
1 q k l
The schema, D, defines the syntax, structure and coding schemes of the output data structure.
6.4.4 Conversion rules
A conversion rule specifies how a data instance in the input data structure shall be converted to zero, one, or
more instances in the output data structure. The conversion rules are defined and based on the concepts of
the conceptual schema language, C, and on the concepts of the output data structure schema, D. It is
necessary to specify a conversion rule, R , for each of the legal combinations of concepts in the conceptual
i
schema language. The set of conversion rules are R  {R , ., R }, where R is the i-th conversion rule and C
1 n i i
is the i-th legal combination of instances from the schema language. A conversion table for all possible C can
i
be set up, where each C maps to a production of instances in the output data structure, D. Figure 2 shows the
i
relationship between the input and output conceptual schema language and the encoding rule.
Output data
Conceptual
structure
schema
schema
language
language
C
D
Encoding
input output
rule
concepts concepts
R
Figure 2 — The encoding rule defines conversion rules from input concepts to output concepts
NOTE The conversion rules are defined based on the two schema languages and not on any particular application
schema. This is a generic approach that allows developers to write application-schema-independent encoding services,
which can be used for different application schemas as long as the schemas are defined in the same conceptual schema
language.
ISO 19118:2011(E)
6.5 Encoding service
An encoding service is a software component that has implemented the encoding rule and provides an
interface to encoding and decoding functionality. It is an integrated part of data interchange.
Figure 3 presents the details of an encoding service and its relationships to important specification schemas.
The encoding service shall be able to read the input data structure and convert the instances to an output data
structure and vice versa. It shall also be able to read the application schema declarations and write the
corresponding output data structure schema. The input data structure is defined by an application schema.
The application schema is defined using concepts of the conceptual schema language. The output data
structure is also described with a schema, called the data structure schema, which defines the possible
content, structure and coding schemes of the output data structure. The data structure schema is described
with a schema language. The encoding rule specifies conversion rules at two levels: the first is at the schema
level and the second is at the instance level. At the schema level, the conversion rules define a mapping for
each of the concepts defined in the application schema to corresponding concepts in the data structure
schema. At the instance level, the conversion rules define a mapping for each of the instances in the input
data structure to corresponding instances in the output data structure. The instance conversion rules are
normally deduced from the schema conversion rules.
Data
Application
structure
Schema
schema
schema
I
D
Encoding
service
Instances
id
input output
Defines
Data flow
Figure 3 — Overview of the encoding process
An encoding service shall at least provide interfaces for encoding and decoding functionality. Examples of
such interfaces are for encoding d  encode (i, I) and for decoding i  decode (d, I). Here, i is a reference to
an application-schema-specific data structure; I is a reference to the application schema; and d is a reference
to the system independent data structure.
6.6 Transfer service
A transfer service is a software component that has implemented one or more transfer protocols that allows
data transfer between distributed information systems over off-line or on-line communication media. To
successfully transfer data between two systems, it is necessary that the sender and receiver agree on the
transfer protocol being used.
Different transfer protocols can be defined. One example is off-line transfer protocols where data are stored
on optical or magnetic media and delivered using postal services or other dedicated delivery services. Another
example is on-line transfer protocols where data are compressed and included as an email attachment,
delivered using a file transfer protocol or transferred using other distributed information technology services
which rely on an underlying network service.
This International Standard does not prescribe any preferred transfer protocols.
10 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
7 Character repertoire
ISO/IEC 10646 defines an internationally recognized repertoire of characters called the Universal Character
Set (UCS) and its character-encoding schemes. The international character set standards defined in
ISO/IEC 10646 shall be used in implementing this International Standard.
The character-encoding schemes that can be supported by international profiles of this International Standard
are the following:
a) 8-bit variable size UCS Transfer Format UTF-8;
b) 16-bit variable size UCS Transfer Format UTF-16;
c) 16-bit fixed size Universal Character Set UCS-2 (deprecated);
d) 32-bit fixed size Universal Character Set UCS-4.
International encoding rules that claim conformance with this International Standard shall support one or more
of these character-encoding schemes. Within national profiles and system implementations, different
character-encoding schemes may be used. The fixed-size character-encoding schemes are often used in
database implementations and the variable-size is often used for data interchange purposes.
ISO/IEC 10646 specifies only the repertoire of characters and gives no indication of which language is actually
used.
NOTE 1 In cases where it is important to distinguish between different languages in text strings, special mechanisms to
indicate the language used can be used.
ISO/IEC 10646 defines mechanisms for creating composite characters. Composite characters are characters
produced by superimposing one or more additional characters on a base character. ISO/IEC 10646 defines a
set of precomposed characters and their defined decomposition. Since mixing composite characters with their
precomposed equivalents can lead to interpretation problems, the use of a composite character if a
precomposed character exists is deprecated, i.e. the precomposed character shall always be used.
To summarize, an encoding rule shall
 support one or more character-encoding schemes, and
 not use composite characters if equivalent precomposed characters exist.
EXAMPLE The precomposed character ö has the defined decomposition o¨.
NOTE 2 For a more detailed description of character normalization, see http://www.unicode.org/reports/tr15/
and http://www.w3.org/TR/charmod-norm/.
NOTE 3 UTF-16, UCS-2 and UCS-4 require information on how to deal with byte ordering,
see http://www.unicode.org/faq/utf_bom.html.
8 Generic instance model
8.1 Introduction
A generic instance model is defined in Clause 8. The instance model is a convenient common representation
of data when developing encoding services. The instance model is capable of representing data described by
application schemas expressed in UML. The instance model represents the application-schema-specific data
structure defined in Clause 6 (data structures i and i in Figure 1). The instance model consists of a dataset
A B
(IM_Dataset) that contains a sequence of objects (IM_Object), where an object consists of a sequence of
properties (IM_Property). Properties in this context are either attributes or associations; operations are not
ISO 19118:2011(E)
included in the general instance model. Each property is encoded according to its data type. The instance
model is shown in Figures 4 and 5.
The application schema defines a number of classes and their attributes and associations and it is the basis
for generating data representations. A data representation (dataset) contains one or more objects that are
structured and encoded according to their class definitions. Clause 8 describes the principles of how to
represent objects, their attributes and associations between objects.
The basic unit of information in a dataset is the object. An object shall be an instance of a single concrete
class. There are no instances of abstract classes and classes stereotyped as interface. Thus, properties
defined by such classes are encoded as part of concrete classes inheriting or realizing them. Each class shall
have a unique name within the application schema. The application schema may refer to or use classes
defined in standardized schemas or other application schemas. The declaration of these classes shall either
be included in the UML model that contains the application schema or accompany the application schema as
a separate file.
An object shall contain a set of property values. The object's class defines the properties and they can either
be inherited through the “class” supertypes or defined within the class itself. In order to differentiate between
the different properties, each property shall have a name that is unique within its class. The property's data
type governs the possible values and the multiplicity statement indicates the number of instances of the
attribute in an instantiated object.
An object has a corresponding class, defined in an application schema or standardized schema, which defines
the possible attributes and associations that are necessary to represent the state of the object. An IM_Object
refers to its class by the “class” attribute, it shall be identified within the context of a dataset by its unique
identifier “id”, and may be universally uniquely identified within a defined universe, application domain or name
space, by its “duid” attribute.
<>
<>
Instance Model::IM_Object
Instance Model::IM_DataSet
object
+ id: CharacterString
+ id: CharacterString
+ duid: CharacterString
0.* 0.*
+ duid: CharacterString
+ /uuid: CharacterString
+ /uuid: CharacterString
+ type: GenericName
constraints
constraints
{uuid = duid}
{uuid = duid}
property 0.*
<>
Instance Model::IM_Property
+ name: GenericName
+ value: IM_Value [0.*] {ordered}

Figure 4 — Instance model — Dataset, object and property
The attributes defined by the class and the association ends navigable from the class are mapped to a set of
properties. A property (IM_Property) represents a name with an ordered collection of values. It can represent
an attribute or association end. The property name shall correspond to the attribute name or the target role
name of an association. A value (IM_Value) represents a property value.
Null values may be given either explicitly or implicitly. An explicit null value shall be indicated by an instance of
the corresponding IM_Property with a given nilReason value. An implicit null value is indicated if the
corresponding IM_Property instance is missing.
12 © ISO 2011 – All rights reserved

ISO 19118:2011(E)
<>
Instance Model::IM_Value
+ id: CharacterString [0.1]
+ duid: CharacterString [0.1]
+ /uuid: Char
...