ETSI GS ARF 005 V2.1.1 (2024-12)

Augmented Reality Framework (ARF); Open APIs for the Creation, Management and Querying of the World Representation

RGS/ARF-005v2.1.1

General Information

• Status: Not Published
• Technical Committee: ARF - Augmented Reality Framework
• Current Stage: 12 - Citation in the OJ (auto-insert)
• Due Date: 10-Dec-2024
• Completion Date: 10-Dec-2024

Standards Content (Sample)

GROUP SPECIFICATION
Augmented Reality Framework (ARF);
Open APIs for the Creation, Management and
Querying of the World Representation
Disclaimer
The present document has been produced and approved by the Augmented Reality Framework (ARF) ETSI Industry
Specification Group (ISG) and represents the views of those members who participated in this ISG.
It does not necessarily represent the views of the entire ETSI membership.

2 ETSI GS ARF 005 V2.1.1 (2024-12)

Reference
RGS/ARF-005v2.1.1
Keywords
API, augmented reality, context capturing and
analysis, interoperability, real world capture
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3 ETSI GS ARF 005 V2.1.1 (2024-12)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definition of terms, symbols and abbreviations . 6
3.1 Terms . 6
3.2 Symbols . 6
3.3 Abbreviations . 6
4 Basic structure of the World Storage API for World Anchors, Reference Objects and
Relocalization Information . 7
4.1 Overview . 7
4.2 Elements for world description . 7
4.3 Structure of the API . 8
5 Description of the API . 9
5.1 Trackables . 9
5.2 World Anchors . 9
5.3 World Links. 10
5.4 Relocalization Information . 10
Annex A (informative): Example Usage of the World Storage API . 11
A.1 Introduction . 11
A.2 Specification of the Validation Application 'Museum' . 11
A.3 World Graph of the Validation Application . 12
A.4 Example Usage of the API (Validation Application) . 12
Annex B (informative): Demonstration of the Authoring of the Validation Application
'Museum' with Unity Plugins . 15
B.1 Introduction . 15
B.2 Authoring the World Storage with Unity Editor windows . 15
B.3 Authoring the World Storage from the Graph View window . 20
History . 24

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4 ETSI GS ARF 005 V2.1.1 (2024-12)
Intellectual Property Rights
Essential patents
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pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI IPR online database.
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
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Foreword
This Group Specification (GS) has been produced by ETSI Industry Specification Group (ISG) Augmented Reality
Framework (ARF).
The ISG ARF shares the following understanding for Augmented Reality: Augmented Reality (AR) is the ability to mix
in real-time spatially-registered digital content with the real world. The present document specifies the interoperability
requirements for Reference Points AR 16 and AR 17 of the reference architecture for AR solutions defined in ETSI
GS ARF 003 [1].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.

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5 ETSI GS ARF 005 V2.1.1 (2024-12)
1 Scope
The present document provides an overview and an introduction to the interface specification for the reference points
"AR 16 - World Anchors" and "AR 17 - Reference Objects" of the AR framework architecture [1] developed by the
ETSI Industry Specification Group (ISG) for an Augmented Reality Framework (ARF). The actual interface
™
specification is provided as OpenAPI specification [3] and forms the baseline for the present document.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found in the
ETSI docbox.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI GS ARF 003 (V1.1.1): "Augmented Reality Framework (ARF) AR framework architecture".
[2] ETSI GS ARF 004-2 (V1.1.1): "Augmented Reality Framework (ARF) Interoperability
Requirements for AR components, systems and services Part 2: World Storage and AR Authoring
functions".
[3] "ARF005 - World Storage API" revision 2.0.0.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] IETF RFC 4122: "A Universally Unique IDentifier (UUID) URN Namespace".
[i.2] IETF RFC 2616: "Hypertext Transfer Protocol HTTP/1.1".
[i.3] OpenAPI™ Specification v3.0.0.
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3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
Augmented Reality (AR): ability to mix in real-time spatially-registered digital content with the real world
AR experience: real time perception of the mixture of the real world and spatially-registered digital content by user
senses
AR system: combination of hardware and software that delivers an AR experience
feature: characteristics of a real world element that can be searched, recognized or tracked ®
NOTE: Features can be of different nature without being limited to visual patterns, UWB, Wi-Fi , Infra Red or
sounds.
pose: combination of position and orientation
reference point: point located at the interface of two non-overlapping functions of the AR framework architecture and
representing interrelated interactions between those functions
trackable: element of the real world of which features are available and/or could be extracted
NOTE: Features can be made available from an analysis of the element itself (fiducial markers, natural images,
3D point cloud) or processed from a representation of the element (3D CAD model).
world anchor: coordinate system related to an element of the real world on which virtual content stays
spatially-registered
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
API Application Programming Interface
AR Augmented Reality
ARF Augmented Reality Framework
CRUD Create Read Update Delete
GUI Graphical User Interface
ISG Industry Specification Group
JSON JavaScript Object Notation
REST Representational State Transfer
UI User Interface
UUID Universally Unique IDentifier
UWB Ultra Wide Band
YAML YAML Ain't Markup Language
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4 Basic structure of the World Storage API for
World Anchors, Reference Objects and
Relocalization Information
4.1 Overview
The World Storage API for World Anchors (AR 16) and Reference Objects (AR 17) allow an AR Authoring function to
store information about World Anchors and Reference Objects (named in the following document and API as
Trackables) in the World Storage at authoring time. This also comprises relative position and orientation information
between Trackables and World Anchors. Afterwards, an AR system processes that data at runtime, e.g. through the
World Analysis function, to provide an AR experience. For this, it retrieves relocalization information from the World
Storage (AR11). This information allows the World Analysis to determine the pose of objects relative to the AR system
or vice versa. This pose can be continuously sent to the Scene Management so that the content of a 3D Rendering
module can be updated in real-time (AR8).
Figure 1 shows the typical use cases for the World Storage within an AR system. The various authoring processes on
the left side of the figure involve real persons (authors) as well as computing services (centre of the figure). While
defining a scenario, authors can use the system in different locations, at different times. The API has to ensure an easy
and elementary access to the World Storage data for creating, managing and deleting World Anchors, Trackables and
their connections (World Links). In addition, the World Storage allows for the retrieval of relocalization information by
the World Analysis. This is shown on the right side of Figure 1. This comprises, e.g. the retrieval of information about
Trackables that can contribute to estimating the pose of a specific World Anchor, which can be determined following
the World Links.
Figure 1: Architecture of a typical AR authoring and World Analysis system
4.2 Elements for world description
A World Graph describes a scene of the real world used at runtime by AR systems to spatially register AR assets with
the real world, ETSI GS ARF 004-2 [2]. It consists of Trackables and World Anchors linked together. Trackables shall
denote information to track objects of the real world. A World Anchor shall represent a pose in the real world in relation
to one or multiple Trackables. World Anchors should be used to attach AR assets at a specific position and orientation
in the real world (see Asset Preparation service in Figure 1). AR assets may also be attached to a Trackable directly, e.g.
to give the trackable a graphical representation.
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To define complex structures and scenarios representing the real world, Trackables and World Anchors should be
linked together with World Links. World Links represent the relative position and orientation between Trackables and
World Anchors. This allows for retrieving from World Anchors all Trackables and their relative positions useful to
estimate the pose of the World Anchors. This World Graph composed of World Anchors, Trackables and their spatial
structure may be considered as a graph representing the real world.
The World Storage API may allow relations as shown by Figure 2 (left side).
Excerpt of World Graphs Acyclic World Graph
World Anchor
World Link
Trackable Trackable
Trackable
World Anchor
World Link
World Anchor World Anchor
Cyclic World Graph
World Link
World Anchor
Trackable World Anchor
Trackable
World Link
World Anchor
Trackable
World Anchor
NOTE: It is recommended to avoid cyclic World Graphs to ease the spatial consistency of Trackables and
World Anchors (see the right side of the figure).

Figure 2: Left: Allowed links between Trackables and World Anchors within a World Graph;
Right: Acyclic vs. cyclic World Graph
4.3 Structure of the API
The World Storage API v2.0.0 is available on the ETSI Forge at following URL:
• https://forge.etsi.org/rep/arf/openapi/-/tree/2.0.0
The OpenAPI yaml file is located here [3]:
• https://forge.etsi.org/rep/arf/openapi/-/blob/2.0.0/API/worldstorage/worldstorageopenapi.yaml
NOTE 1: The world storage OpenAPI yaml file depends on a OpenAPI file defining common schemas shared with
the World Analysis OpenAPI.
• https://forge.etsi.org/rep/arf/openapi/-/blob/2.0.0/API/common/commonopenapi.yaml
™
The structure of the file is based on the OpenAPI 3.0.0 specification [i.3].
The file has 4 main parts:
• Header part (copyrights, info, servers, tags, etc.).
• Paths for administration (/ping, /admin, /version).
• Paths for the objects of the world (/trackables, /worldAnchors and /worldLinks) - for the description of the
actions (REST) and return values.
• Path for the retrieval of the localization of selected objects of the World (/relocalizationInformation) - also
for the description of the actions (REST) and return values.
• Components part - containing the various schemas (in/out parameters).
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The common file has a single part:
• Components part - containing various common schemas (in/out, mode and geometry parameters) and HTTP
responses (client and server errors, warnings). All responses are now packaged into a schema with a separate
"message" string component.
JSON should be used as coding protocol for parameter object structures and return values.
NOTE 2: Information about the definition and the characteristics of UUIDs can be found in IETF RFC 4122 [i.1].
The HTTP semantics are described in IETF RFC 2616 [i.2].
The administration paths can be used to test a server, to get the state of a server, and to request the API version.
The API may be tested in the "rendered file" view on the ETSI Forge, directly from the repository.
An implementation of the API shall follow the specification in the linked OpenAPI yaml file.
5 Description of the API
5.1 Trackables
The OpenAPI path /trackables in the YAML file " worldstorageopenapi.yaml" defines the CRUD operations Create
(POST), Read (GET), Update (PUT) and Delete (DELETE) for the Trackables (described in the AR Framework
architecture document ETSI GS ARF 003 [1] as the reference point "AR 17-Reference Objects").
Operations:
• Creating and updating a Trackable returns the UUID of the Trackable.
• Accessing one Trackable by UUID returns a JSON document containing the information about that Trackable.
• Accessing all Trackables returns a JSON list of all Trackables.
• Deleting one Trackable (by UUID) removes it from the World Storage.
By deleting a Trackable, the World Storage server shall update all World Links referring this Trackable.
A server shall implement all operations for managing Trackables. Anyway, it may refrain from accepting operation
calls for creating updating and deleting Trackables to prevent unauthorized changes in the database.
NOTE: See https://forge.etsi.org/rep/arf/openapi/-/blob/2.0.0/API/worldstorage/worldstorageopenapi.yaml#L144.
5.2 World Anchors
The OpenAPI path /worldAnchors in the YAML file " worldstorageopenapi.yaml" defines the CRUD operations
Create (POST), Read (GET), Update (PUT) and Delete (DELETE) for the World Anchors (described in the AR
Framework architecture document ETSI GS ARF 003 [1] as the reference point "AR 16-World Anchors").
Operations:
• Creating and updating a World Anchor returns the UUID of the World Anchor.
• Accessing one World Anchor by UUID returns a JSON docu
...