ISO/TR 19115-4:2026

Technical
Report
ISO/TR 19115-4
First edition
Geographic information —
2026-10
Metadata —
Part 4:
JSON schema implementation of
metadata fundamentals
Information géographique — Métadonnées —
Partie 4: Mise en œuvre des principes fondamentaux des
métadonnées par des schémas JSON
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Basic approach and design decisions. 1
4.1 Overview .1
4.2 General approach and workflow .1
4.3 JSON representation .2
4.4 Profile on conceptual content .3
4.5 ISO 19115-4 (this document) UML and ISO 19157-1 UML implementation models for
JSON .3
4.6 JSON reference instance document .4
4.7 UML to JSON encoding rules and automated generation of JSON schema .5
4.8 Multilingual adaptability .5
5 Encoding approach and rules . 5
5.1 UML to JSON encoding rules .5
5.1.1 Overview .5
5.1.2 General rules for transforming UML to JSON schema .5
5.1.3 Details and deviations .5
5.1.4 Code lists .7
5.1.5 Missing JSON base types .8
5.2 Modularization .9
5.3 UML implementation model for JSON implementation.10
Annex A (informative) Defined profile (subset) on ISO 19115-1 and ISO 19157-1 .12
Annex B (informative) Geographic metadata JSON schema resources .17
Annex C (informative) Implementation example .18
Bibliography . 19

iii
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 211, Geographic information/Geomatics, in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 287,
Geographic Information, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement), and in collaboration with the Open Geospatial Consortium (OGC).
A list of all parts in the ISO 19115 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
[1]
ISO 19115-1 explains the importance of metadata, specifies a model for describing geographic information
resources by defining metadata entities, elements and terminology, and establishes an extension procedure
for additional metadata content. This document investigates the JSON implementation of this same
[2]
conceptual model including relevant parts of ISO 19157-1 . A resulting JSON encoding is developed for
a subset of the named conceptual models showing the principles used. In this regard the defined JSON
encoding is not intended to be a formal JSON encoding but serves as a proof of concept.
The primary use case envisioned for the JSON implementation illustrated in this document is the exchange
and publication of geographic metadata through APIs. The intention in publishing this document is that the
community can begin using this approach and can feed back improvements so that a formal specification
can be developed.
JSON has become one of the major encodings used by current web applications, for example in many
implementations of OGC API Records. A JSON encoding to standardize a JSON implementation of metadata
[1]
types is needed. This document describes a JSON encoding of ISO 19115-1 including the data quality
[2]
concepts in ISO 19157-1 . In this document only a subset of both standards is implemented. A subset,
considered to be the core part of both standards, currently satisfies the need for an initial evaluation and
proof of concept for the JSON encoding. This document and the resulting JSON encoding are regarded as
mature within the context of an ISO technical report, encompassing a broad range of content. In the future,
the scope will potentially be expanded to include the complete content of the ISO 19115 series conceptual
models.
[1] [2]
The integrated JSON schema was derived from the ISO 19115-1 and ISO 19157-1 conceptual models in
UML. Since standardized UML-to-JSON encoding rules do not yet exist, the OGC document Best Practice for
[3]
OGC - UML to JSON Encoding Rules was used as a reference.
This implementation model described in this document does not alter the semantics of the source conceptual
models, but profiles content required for efficient JSON implementation and adds tagged values to the UML
to facilitate UML to JSON transformation software. The JSON schemas were created automatically from
the UML model, based on UML to JSON encoding rules as well as on a manually generated JSON reference
instance document. Automated generation is according to the encoding rules described in OGC best practice
[3]
report: Best Practice for OGC - UML to JSON Encoding Rules. The JSON reference instance document was
[4]
created based on a manually created ISO 19115-3 XML document. The name and contact information of
the maintenance agency for this document can be found at www.iso.org/maintenance_agencies.

v
Technical Report ISO/TR 19115-4:2026(en)
Geographic information — Metadata —
Part 4:
JSON schema implementation of metadata fundamentals
1 Scope
[5] [1] [2]
This document describes a ECMA 404:2017 JSON implementation of ISO 19115-1 and ISO 19157-1 as
a proof of concept. The resulting JSON encoding is not a formal json specification but is intended to proof the
feasibilty of the approach taken and the implicated encoding principles.
[6]
The document provides a set of JSON schema files which define a JSON encoding of the concepts defined by
[1] [2]
conceptual schemas in ISO 19115-1 and ISO 19157-1 . The JSON representation is scoped to exchange via
[1] [2]
HTTP. In this document, only a subset of the content of both ISO 19115-1 and ISO 19157-1 is included, in
order to simplify the process of defining the resulting JSON schema. For the same reason, ISO 19115-2:2019
[7] [1]
is currently not included. The subset is chosen to be a core operational set of both ISO 19115-1 and
[2]
ISO 19157-1 .
This document describes the procedure used to generate JSON schema from ISO geographic information
conceptual models related to metadata. The procedure includes creation of an UML implementation model
[1] [2]
for JSON implementation derived from the ISO 19115-1 and ISO 19157-1 conceptual schemas.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Basic approach and design decisions
4.1 Overview
This clause describes the approach that was taken to generate the metadata JSON schema. The approach
consists of a workflow identifying several steps. The workflow and the separate steps are described and
include formulated design decisions and requirements set for the JSON schema to be produced.
4.2 General approach and workflow
A general approach and workflow has been followed to guide the process for the realization of the JSON
schemas and the related document. This workflow was based on a combination of requirements and
decisions that are explained in the following subclauses. Figure 1 explains the approach and workflow and
shows six steps and several products.

Figure 1 — Schematic view of general approach and workflow
[1] [2]
— Step 1a) — The conceptual schemas of ISO 19115-1 and ISO 19157-1 are the conceptual input for the
[2]
UML implementation model for JSON described in ISO 19157-1 and in this document. For ISO 19157-1
[2]
, a JSON implementation model is developed only from the perspective of this document. This means
that for this document, no overall evaluation of the ISO 19157 series elements is included. This can be
anticipated in a separate, future ISO 19157 series of JSON implementation.
— Step 1b) — A JSON reference dataset is created that defines the preferred JSON encoding against which
the generated JSON schemas were tested and improved.
— Step 2) — The UML implementation model described in this document is input for an automated and rule-
[2]
based transformation to a JSON schema encoding. Since ISO 19157-1 is referenced from this document,
this is also transformed to a JSON schema.
— Step 3) — The generated JSON schemas are tested against the JSON reference dataset. In an iterative
process, results of this test are fed back to adapting the UML implementation models and/or
[2]
transformation parameters of this document and ISO 19157-1 . The updated JSON schemas are
tested again. Requirements set by the JSON reference dataset that cannot be met by automated schema
generation and existing encoding rules are adapted manually.
— Step 4) — The JSON reference dataset is verified against the JSON schemas and vice versa and the schema
is accepted for publication.
[2]
— 5)  The verified JSON schemas for this profile of this document and ISO 19157-1 are published as a
resource of this document.
Detailed descriptions of these steps are presented in the following subclauses.
4.3 JSON representation
For the JSON representation to encode ISO 19115-4 several specific choices are made.
[8]
A MD_Metadata record is represented as a IETF RFC 7946:2016 GeoJSON feature. The following points
apply:
— the metadata identifier is set as the "id" member;
— the spatial extent is in the "geometry" and/or "bbox" members;
— all other properties of the record are in the "properties" member;
— when the MD_Metadata does not have a spatial reference, i.e. no spatial extent is present, the geometry
member is set to null;
— it is recognized that GeoJSON uses only WGS84 as coordinate reference system. In cases where this is not
appropriate, for instance when data cannot be referenced to the Earth, the geometry member can be set
to null.
The structure of the properties is in general a straightforward mapping of the UML model to JSON:
— properties with structured values (data types, classifiers) are mapped to a JSON object;
— all other properties are mapped to the JSON types string, number or boolean;
— properties with a maximum multiplicity greater than one are wrapped in a JSON array.
[9]
This representation has similarities with the XML representation specified by the ISO/TS 19139-1
encoding rule. The main differences are as follows.
— The JSON representation is "flatter" as in XML an extra tag is used for each object, grouping the tags of
each property, while in JSON simply a JSON object is used. In cases where the type of the object is unclear,
since multiple instantiable types can be the property value due to the use of inheritance in the model, an
additional member "type" is added with the name of the type in the model. In XML the type is expressed
in the name of the tag of the object.
— The XML representation also represents base types like a string as an object to support representing
sub-types, which is an edge case, while the JSON representation removes this capability to simplify the
use of the data.
— The XML encoding rules in the ISO 19139 series added a capability to add metadata to a property without
value. This capability is not included in the conceptual model and has not been included in the JSON
representation.
More details of the encoding rule for representing a MD_Metadata record is provided in 4.6.
The reason for this representation is that GeoJSON is the most widely supported JSON format for spatial data.
As a result, those metadata records in JSON that include a spatial extent (at least those metadata records
that include a geographic extent) can be shown on a map in almost all mapping tools and libraries .
[10]
Those that want to link members of a JSON document to an ontology can add a JSON-LD context to the
JSON instance. Nesting capabilities are also available thanks to the support of JSON-LD at core level.
4.4 Profile on conceptual content
[1]
The source of the conceptual content are the conceptual models as described by ISO 19115-1 and the
[2]
data quality standard ISO 19157-1 . Nesting capabilities are also available thanks to the support of JSON-
LD at core level. However, to handle complexity in this phase and first get a working operational JSON
implementation, which can be reviewed and later extended, the input conceptual models are profiled or sub-
setted to a selection of metadata classes.
The requirements for this subset were set to meet two criteria: that the subset covers most of the common
use of metadata defined in the ISO 19115 series, and that the subset excludes complex constructs that
currently do not add much to the applicability of this JSON implementation. The profile is called "ISO 19115-4
Core".
[1] [2] [11]
"ISO 19115-4 Core" is defined by a profile on ISO 19115-1 and ISO 19157-1 . No content of ISO 19115-2
[1] [2]
is included in this 19115-4 Core. For ISO 19115-1 and ISO 19157-1 , the subset is described in Annex A.
4.5 ISO 19115-4 (this document) UML and ISO 19157-1 UML implementation models for
JSON
Two UML implementation models were created:
— ISO 19115-4 Core
— ISO 19157-1 Core
[1] [2]
The ISO 19115-4 Core JSON was created based on the ISO 19115-1 conceptual model. For ISO 19157-1 ,
the ISO 19157-1-core JSON was created. These UML implementation models define the ISO 19115-4 Core
[4]
profile and serve as an input for automated JSON schema derivation. The ISO 19115-3 implementation
model was not used as it is an XML implementation profile. The ISO 19115-4 Core UML implementation
model is intentionally a straight forward copy of the conceptual models. Specifications are only added at
the level of UML tagged values to steer the automated JSON schema generation. The advantage of this is an
easier maintenance relation between conceptual and implementation model.
4.6 JSON reference instance document
It was concluded that a straightforward rule-based generation of JSON schemas from the ISO 19115-4
Core UML implementation model did not result in a JSON schema optimized for an efficient JSON data
implementation.
There were two main reasons:
— JSON schema does not support the concept of type inheritance. There are ways to represent type
inheritance in JSON schema, but they all have their advantages and disadvantages depending on how
type inheritance is used in the model. A consequence is that it is often beneficial to modify the JSON
representation on a case-by-case basis.
— In some cases, for example, the uses of CI_Date, a direct mapping of the conceptual model results in an
unnecessarily complex JSON representation that could be improved (in general, the conceptual model
could be improved in those cases, too; in the CI_Date case, a qualified association to DateTime with the
dateType as the qualifier expresses the semantics more accurately than the current model).
To agree on an efficient JSON data implementation a JSON reference instance document was created.
This JSON reference instance document was used to adapt the rules and specifications for automatically
generating a JSON schema from the ISO 19115-4 Core implementation model.
NOTE These adaptations will be proposed to OGC for a revision of their Best Practice document.
The JSON reference instance document was created manually on the basis of an existing and adapted
[4]
ISO 19115-3 XML dataset. This XML dataset was chosen from an existing metadata dataset and adapted
[4]
to cover the most common operational part of the ISO 19115-3 implementation model and therefore
reflecting a good representation of the planned content of the ISO 19115-4 Core. In Annex A, the classes
contained in the JSON reference instance document are presented and related to the core profile. In Annex C
the JSON reference instance document is presented.
The creation of the reference instance document led to a first list of basic requirements:
a) MD_Metadata is the starting object of a JSON metadata document. This MD_Metadata object will be
encoded as a GeoJSON feature collection or feature (when the metadata only refers to a single area). This
approach makes a JSON metadata document implementable in a GeoJSON environment.
b) All properties of a MD_Metadata record are encoded in the "properties" object of that GeoJSON feature.
The relevant geometry properties will be mapped to the GeoJSON feature geometry elements.
c) The default encoding of associations will be inline. By-reference encoding will only be specified where
the inline option is not appropriate, typically because of re-use or recursive inline inclusions.
d) One or only a limited set of JSON schemas is preferred as this will provide a simpler schema handling.
[1] [2]
The modularization as is found in the ISO 19115-1 andISO 19157-1 conceptual models will not be
expressed in separate JSON schemas.
e) Tailoring a JSON metadata schema for specific profiles can be done as a separate process. This is not
part of this document.
4.7 UML to JSON encoding rules and automated generation of JSON schema
The UML to JSON encoding started with rules from the Best Practice for OGC - UML to JSON encoding
[3] [12]
rules . This comprises encoding rules to plain JSON, GeoJSON and JSON-FG 0.1 and is considered to be
a mature specification in this domain. The ISO 19115-4 Core implementation model was used as input in
UML to JSON schema transformation software implementing the mentioned encoding rules. As remarked in
4.6, the result was not an optimal JSON schema for efficient JSON data implementation. Testing the results
against the content and structure of the JSON reference instance document led to updated conversion rules,
adapted transformation settings and some manual reworking of the ISO 19115-4 Core JSON schema. These
deviations from the defined encoding rules are documented in 5.1.3.
4.8 Multilingual adaptability
The web architecture and HTTP support access to content in a specific language which is applicable to most
multilingual situations envisaged for the ISO 19115 series.
JSON is generally used within a web context. Both web architecture and JSON have native ways to handle
multiple languages which are applicable to most multilingual situations envisaged for the ISO 19115 series.
For example, in this specific case of localized text: On the web, a resource representation is typically in a
[13]
single language, expressed via Reference the "Content-Language" header. At the back-end, the resource
can be (and often is) multilingual. When requested via HTTP, the result is a representation in a single
language. The language will be determined based on the request (e.g. a language-specific URL or an "Accept-
Language" header).
If used in a web context there is no need for a LocalisedCharacterString in JSON. The language used in the
particular JSON document / representation is represented by the "Content-Language" header and maybe
also a property that could be added to the JSON object itself.
5 Encoding approach and rules
5.1 UML to JSON encoding rules
5.1.1 Overview
The encoding of the ISO 19115-4 Core metadata UML implementation model into JSON schema is rule-based.
Encoding rules are used and or defined to encode the the UML model into a resulting JSON schema. In this
clause, several aspects are described that led to a final set of rules for the UML to JSON schema encoding, as
well as rules that describe conversion rul
...