PROPOSED Web-based Digital Twins for Smart Cities Interest Group Charter

The mission of the Web-based Digital Twins for Smart Cities Interest Group is

Join the Web-based Digital Twins Interest Group.

This proposed charter is available on GitHub. Feel free to raise issues.

Charter Status See the group status page and detailed change history.
Start date [dd monthname yyyy] (date of the "Call for Participation", when the charter is approved)
End date [dd monthname yyyy] (Start date + 2 years)
Chairs [chair name] (affiliation)
Team Contacts Kazuyuki Ashimura (0.2 FTE)
Meeting Schedule Teleconferences: Regular weekly calls will be held.
Face-to-face: we will meet during the W3C's annual Technical Plenary week; additional face-to-face meetings may be scheduled by consent of the participants, usually no more than 3 per year.
Workshop: A workshop with an open CFP and invited speakers may be organized to provide further feedback and input and the guide the group's agenda.

Note: The W3C Process Document requires “The level of confidentiality of the group's proceedings and deliverables”; however, it does not mandate where this appears. Since all W3C Working Groups should be chartered as public, this notice has been moved from the essentials table to the communication section.

Motivation and Background

Initial discussion during the Smart Cities Workshop in 2021

"Smart Cities" refers to a range of technologies and processes for intelligent management of our built and inhabited environment. As interest rises, we see prospects for smarter and easier integration of various technologies from multiple vendors related to IoT devices and Web services.

Several preliminary use cases on Smart Cities have been discussed within the Web of Thing (WoT) IG as part of the WoT standardization based on the proposal during the Second WoT Workshop in Munich.

However, Smart Cities include various technologies, of which WoT is just one. So W3C organized a virtual online workshop on Smart Cities in June 2021 to finalize this Charter for the Smart Cities Interest Group to collect input from the Smart Cities stakeholders.

During the workshop discussion, we did the following:

Follow-up discussion during the TPAC 2022 breakout, etc.

Follow-up discussion on Web-based Digital Twins for Smart Cities was organized at (1) the breakout session during TPAC 2022 in Vancouver, Canada and (2) another breakout session during TPAC 2023 in Seville, Spain, and representatives from the following standardization organizations discussed the current situation and problems of their standardization work on Smart Cities:

As a consequence, the participants identified that "Digital Twins" would be the key concept to handle Smart Cities services in a standardized manner, and got consensus to continue further discussion on a possible framework of Web-based Digital Twins for Smart Cities within the W3C to cope with remaining issues of Smart Cities.

What has been done so far

W3C Web of Things

IoT developers face the big problem of “IoT Silos” when creating an application including multiple services from different IoT platforms.

IoT Silos
IoT Silos

The W3C Web of Things (WoT) Working Group has been working on standards to counter the fragmentation of the IoT and enable easy integration of IoT devices and services across IoT platforms and application domains by providing a common description across different ecosystems (=WoT Thing Description), standards.

Interconnection using WoT
Interconnection of IoT platforms using WoT as a hub

WoT standards are now being used for various industry areas including the following:

Smart home (collaboratively with ECHONET)
Improve the usability of home appliances for device users by allowing device users to configure the operation modes of all devices at home without configuring those devices one by one when they leave and come home.
Smart building (collaboratively with IPA DADC)
Integrate various sensor networks and various devices by WoT within a smart building which use different data models and protocols.
Smart factory (collaboratively with OPC Foundation's OPC UA (Uivied Architecture))
A bottling line consists of a filling module, a capping module, a labeling module, and a transport system. The production line is provided via an OPC UA endpoint for control and monitoring purposes.

Related SDO's work

IEC SC3D's Common Data Dictionary (CDD)
Defining common methodology and product ontology for various IoT purposes.
Various standards on smart cities and digital twins, e.g., ISO/IEC 30146:2019
Standardization on IoT and Smart Cities from the ICT viewpoint, e.g., Data Processing and Management (FG-DPM)
Open Geospatial Consortium (OGC)
Geospatial standards and tools around smart cities and digital twins

What is still missing?

During the discussions so far, there are strong needs for the followings:

“Digital Twins” as the Key Concept

During the discussions at the TPAC 2022 breakout, it was identified “Digital Twins” would be the key concept for Smart Cities services, and we should start with clarifying the use cases and requirements for “Digital Twins” first.

Note that there are various definitions for "Digital Twins" all over the world. However, given the collaborative discussion with ITU-T SG20 and ISO/IEC JTC 1/WG11 starting with the Smart Cities Workshop, we'd like to use the following basic definition from "Y.4605" as the starting point.

Basic Definition of "Digital Twins"

A digital twin is the digital representation of an object of interest with data connection that enables convergence between the physical state and digital state at an appropriate rate of synchronization. The digital twin has been applied in various industry domains including manufacturing, transportation, energy, firefighting, medical and safety.

- ITU-T Y.4605: Information exchange model for digital twin federation in smart cities and communities, ITU-T SG20 (in liaison with ISO/IEC JTC 1/SC 41, JTC1/WG11)
Digital Twins
Digital Twin Framework

Digital Twin framework provides a method to applications to handle physical devices by controlling the digital representations of the physical devices on the digital layer based on the data connection between the digital representations and the physical devices.

A possible data connection mechanism for Web-based Digital Twins, which was agreed on during the TPAC 2022 breakout, consists of the following three W3C standards:

Possible Web-based Digital Twin Platform
Possible Web-based Data Connection Framework for Digital Twins

During the group's discussion, we’ll see the other existing definitions of "Digital Twins" from the other SDOs and actual Smart Cities, and work on further clarifications about the definition of “Web-based Digital Twins”.


Scope Summary

  • Identification of stakeholders from the industries, countries/cities and communities to involve in the group's discussion
  • Survey on the existing technologies and standards for Smart Cities, e.g., possible building blocks of Digital Twin Framework and standardized Vocabularies for Smart Cities
  • Best Practices on what kind of technologies to be applied to what kind of Smart Cities applications, e.g., WoT, Automotive, Geospatial, VR/AR, Speech and Semantic Web to be applied to improved accessibility, visitor guidance and energy management
  • Use cases and requirements for Smart Cities

Standards are essential for Smart City technology and business development. Standards benefit vendors, cities, and users. For vendors, standards unify markets and mean that a larger market can be addressed with a single product design, allowing products to more efficiently make returns on the investments needed to develop them. For cities, standards allow the deployment of technologies that can be sourced from multiple vendors, more and higher quality products, and increases the probability that systems will remain usable over a longer timescale. Standards also encourage the development of open systems that can interoperate with other standardized systems, multiplying the number of use cases that can be addressed. For users, standardized technologies mean that services available in one city will also be available in others, facilitating mobility.

However, we need to know what standards should be developed to achieve these objectives. What gaps exist? What opportunities can be exposed by standards that enable new use cases? What are the business drivers that encourage adoption of standards, and how can standard development be aligned with these drivers? Given a set of standards that could be developed, what are the priorities? How can the needs and goals of all stakeholders be aligned?

The purpose of this Interest Group is collect and connect Smart City stakeholders to answer these kinds of questions and drive the development of Web technology standards aligned with the real needs of Smart Cities.

The topics that the Interest Group will address include but are not limited to:

We can speculate about many topics, so need to identify what the group's key topics are and see what would fit with W3C through the discussion with the existing smart cities. Note that the topics listed above are related to each other, so the relationship among multiple topics should be described as concrete use cases, e.g., which topics to be considered in what kind of situation.

The main tasks that the Interest Group will undertake include:

The group should also consider the following when work on the above tasks:

Accessibility is very important for smart cities because cities include many people potentially with disabilities. So we need to look for "missing data" within smart cities, i.e., data of those who might not be well-represented among the data-sets, to ensure that they are surely recognized and well-served by the smart cities. For that purpose, we need to consider people with multiple disabilities (intersectional considerations) and people with cognitive and learning disabilities too.

Note that there are many topics to discuss around Smart Cities and the scope of the group may become too broad. So we'd like to start with discussion about the following two points:

  1. what a Web-based Digital Twin framework for for Smart Cities should be like based on the possible Web-based Data Connection Framework for Digital Twins in section 1.6 "Digital Twins” as the Key Concept" above
  2. standardized vocabulary for Smart Cities based on the feedback from the Smart Cities stakeholders including the related SDOs and actual Smart Cities

The goal of the group is not to generate standard itself, but to gather pain points, requirements and priorities for Web-based smart cities in the near future. So we need to figure out the focus that W3C can make the most impact. We don't want to duplicate work already done by the other SDOs.

Out of Scope

The technical development of standards is not in scope for the Interest Group. Technical discussions are expected to take place within a new or existing W3C Working Groups, or within a Community Group or Business Group when incubation is needed.


The primary deliverables of the Smart Cities Interest Group will be IG Notes that identify requirements for existing and/or new technical specifications and gaps in the Web Platform.

Normative Specifications

The Interest Group will not deliver any normative specifications.

Other Deliverables

Other non-normative documents may be created such as:

  • Survey on the existing technologies and standards for Smart Cities (Technology Landscape)
  • Best Practices on what technologies, e.g., WoT, Automotive, Geospatial, VR/AR, Speech and Semantic Web, to be applied for what kind of Smart Cities applications, e.g., improved accessibility, visitor guidance and energy management.
  • Use cases and requirements for Smart Cities


The IG will, during its lifetime, undertake different activities that may proceed in parallel. No specific timeline has been identified at this point, but the various activities are intended to be running for short periods of time (2-12 months), with the possibility of running a few iterations of them.

Success Criteria

Smart Cities vary widely and diversely. So we can wander into all sorts of areas if we don't get the right regulators to hear where they care. Therefore we need to make sure the group enrolls the support of implementors, the authorities and cities to get them involved to help set prioritization.

For that purpose, we need to identify important stakeholders and would start with a smaller team, e.g., Asian stakeholders like Singapore, Japan, China and Korea, and involve more countries/cities like Sweden, Brazil and NYC via the collaboration with the W3C Chapters and the attendees of the Smart Cities Workshop in June 2021 and the TPAC breakout sessions in October 2021 (Day 1, Day 2).

The Interest Group will have succeeded if it can achieve the following:


For all deliverables, this Interest> Group will seek horizontal review for accessibility, internationalization, privacy, and security with the relevant Working and Interest Groups, and with the TAG. Invitation for review must be issued during each major standards-track document transition, including IG Note. The Interest Group is encouraged to engage collaboratively with the horizontal review groups throughout development of each deliverable. The Interest Group is advised to seek a review at least 3 months before first entering IG Note and is encouraged to proactively notify the horizontal review groups when major changes occur in a specification following a review.

Additional technical coordination with the following Groups will be made, per the W3C Process Document:

W3C Groups

Web of Things (WoT) IG/WG/CG/JP-CG
internet of things, discovery, edge computing
Decentralized Identifiers (DID) WG / Verifiable Credentials (VC) WG / Credentials CG
identifiers, signing, credentials, authentications
Accessible Platform Architectures (APA) Working Group
provide accessibility use cases for smart cities in addtion to ordinary accessibility review
Media and Entertainment IG
signage, video links
Web and Networks IG
edge computing, network metadata
Publishing BG / Publishing CG / EPUB 3 WG / Publishing WG
documentation, public communications, multimedia
Automotive Ontology CG
ontologies for automotive purposes
Automotive Privacy Principles CG
privacy around connected cars
Spatial Data on the Web IG
Dataset Exchange WG
(geolocation, semantics, data modelling)
Immersive Web WG
GPU for the Web WG
ML, DL, edge computing
Big Data CG
data management, data modelling
Voice Interaction CG
Voice agents for smart user interface
Solid CG
Mechanisms to share private data in a controlled way
Agriculture CG
definition of agriculture use cases
Linked Building Data CG
Relationship with smart buildings as part of the geolocation use cases
Web Authentication WG
security, credentials
Service Workers WG
edge computing
Devices and Sensors (DAS) WG
JSON-LD WG / JSON for Linking Data CG
data modelling, semantics
Web Payments WG/Web Payment Security IG
Web Real-Time Communications WG
video and data streams
Web Assembly WG
edge computing
Accessible Infographics CG
data visualization

External Organizations

SDOs working on Smart Cities:
communication protocols, data modelling, discovery, and security standards
standards for telecommunication technologies and the use cases they enable
Open Geospatial Consortium (OGC):
geolocation and geographic information systems
standards on sustainable cities and communities
standardized vocabulary for smart cities
standards on smart city ICT, pre-research work and gap analysis
trusted framework to support smart cities and communities
standardization to meet citizen and consumer requirements
open-source implementations of open standard like NGSI-LD in partnership with ETSI, etc.
standardized taxonomy, terminology and semantics for smart cities
smart homes
IPA (Information-technology Promotion Agency, Japan) DADC
smart buildings
foundation for transparency, legibility and accountability of digital technology in built environment
OPC Foundation
smart devices and privacy management
Economic Unions and Communities (not limited to but including the following):
Discussion of smart city use cases and deployments in South-East Asia.
The World Economic Forum
improving the state of the world by engaging business, political, academic, and other leaders
The Smart City Consortium
smart city discussion in Hong Kong, and share the expertise with other professional bodies
The Smart Cities Council
building cross-sector capability, capacity and collaboration around smart cities
TM Forum
alliance of 800+ global companies working together to break down technology and cultural barriers
Viable Cities
climate Neutral Cities 2030 with a good life for all within the limits of the planet
Other economic unions and communities to be added
Countries and Cities:
  • Japan
  • China
  • Korea
  • Singapore
  • United States
  • United Kingdom
  • Brazil
  • Other countries and cities to be added including developing countries and rural areas


To be successful, this Interest Group is expected to have 6 or more active participants for its duration, including representatives from the key implementors of this specification, and active Editors and Test Leads for each specification. The Chairs, specification Editors, and Test Leads are expected to contribute half of a working day per week towards the Interest Group. There is no minimum requirement for other Participants.

The group encourages questions, comments and issues on its public mailing lists and document repositories, as described in Communication.

The group also welcomes non-Members to contribute technical submissions for consideration upon their agreement to the terms of the W3C Patent Policy.

Participants in the group are required (by the W3C Process) to follow the W3C Code of Conduct.


Technical discussions for this Interest Group are conducted in public: the meeting minutes from teleconference and face-to-face meetings will be archived for public review, and technical discussions and issue tracking will be conducted in a manner that can be both read and written to by the general public. Working Drafts and Editor's Drafts of specifications will be developed in public repositories and may permit direct public contribution requests. The meetings themselves are not open to public participation, however.

Information about the group (including details about deliverables, issues, actions, status, participants, and meetings) will be available from the Web-based Digital Twins for Smart Cities Interest Group home page.

Most Web-based Digital Twins for Smart Cities Interest Group teleconferences will focus on discussion of particular specifications, and will be conducted on an as-needed basis.

This group primarily conducts its technical work on GitHub issues (LINK To be updated). The public is invited to review, discuss and contribute to this work.

The group may use a Member-confidential mailing list for administrative purposes and, at the discretion of the Chairs and members of the group, for member-only discussions in special cases when a participant requests such a discussion.

Decision Policy

This group will seek to make decisions through consensus and due process, per the W3C Process Document (section 5.2.1, Consensus). Typically, an editor or other participant makes an initial proposal, which is then refined in discussion with members of the group and other reviewers, and consensus emerges with little formal voting being required.

However, if a decision is necessary for timely progress and consensus is not achieved after careful consideration of the range of views presented, the Chairs may call for a group vote and record a decision along with any objections.

To afford asynchronous decisions and organizational deliberation, any resolution (including publication decisions) taken in a face-to-face meeting or teleconference will be considered provisional. A call for consensus (CfC) will be issued for all resolutions (for example, via email, GitHub issue or web-based survey), with a response period from one week to 10 working days, depending on the chair's evaluation of the group consensus on the issue. If no objections are raised by the end of the response period, the resolution will be considered to have consensus as a resolution of the Interest Group.

All decisions made by the group should be considered resolved unless and until new information becomes available or unless reopened at the discretion of the Chairs.

This charter is written in accordance with the W3C Process Document (Section 5.2.3, Deciding by Vote) and includes no voting procedures beyond what the Process Document requires.

Patent Disclosures

The Interest Group provides an opportunity to share perspectives on the topic addressed by this charter. W3C reminds Interest Group participants of their obligation to comply with patent disclosure obligations as set out in Section 6 of the W3C Patent Policy. While the Interest Group does not produce Recommendation-track documents, when Interest Group participants review Recommendation-track specifications from Working Groups, the patent disclosure obligations do apply. For more information about disclosure obligations for this group, please see the licensing information.


This Interest Group will use the W3C Software and Document license for all its deliverables.

About this Charter

This charter has been created according to section 3.4 of the Process Document. In the event of a conflict between this document or the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Charter History

The following table lists details of all changes from the initial charter, per the W3C Process Document (section 4.3, Advisory Committee Review of a Charter):

Charter Period Start Date End Date Changes
Initial Charter [dd monthname yyyy] [dd monthname yyyy] none

Change log

Changes to this document are documented in this section.