Frequently Asked Questions

Abreviations

Term	Full Form
DT	Digital Twin
DTaaS	Digital Twin as a Service
PT	Physical Twin

General Questions

What is DTaaS?

DTaaS is software platform on which you can create and run digital twins. Please see the features page to get a sense of the things you can do in DaaS.

Are there any Key Performance / Capability Indicators for DTaaS?

Key Performance Indicator	Value
Processor	Two AMD EPYC 7443 24-Core Processors
Maximum Storage Capacity	4TB SSD, RAID 0 configuration
Storage Type	File System
Maximum file size	10 GB
Data transfer speed	100 Mbps
Data Security	Yes
Data Privacy	Yes
Redundancy	None
Availability	It is a matter of human resources. If you have human
resources to maintain DTaaS round the clock,
upwards 95% is easily possible.

Do you provide licensed software like Matlab?

The licensed software are not available on the software platform. But users have private workspaces which are based on Linux-based xfce Desktop environment. Users can install software in their workspaces. The licensed software installed by one user is not available to another user.

Digital Twin Models

Can DTaaS create new DT models?

DTaaS is not a model creation tool. You can put model creation tool inside DTaaS and create new models. The DTaaS itself does not create digital twin models but it can help users create digital twin models. You can run Linux desktop / terminal tools inside the DTaaS. So you can create models inside DTaaS and run them using tools that can run in Linux. The Windows only tools can not run in DTaaS.

How can DTaaS help to design geometric model? Does it support 3D modeling and simulation?

Well, DTaaS by itself does not produce any models. DTaaS only provides a platform and an ecosystem of services to facilitate digital twins to be run as services. Since each user has a Linux OS at their disposal, they can also run digital twins that have graphical interface. In summary, DTaaS is neither a modeling nor simulation tool. If you need these kinds of tools, you need to bring them onto the platform. For example, if you need Matlab for your work, you need to bring he licensed Matlab software.

Commercial DT platforms in market provide modelling and simulation alongside integration and UI. DTaas is not able to do any modelling or simulation on its own like other commercial platforms. Is this a correct understanding?

Yes, you are right

Can DTaaS support only the information models (or behavioral models) or some other kind of models?

The DTaaS as such is agnostic to the kind of models you use. DTaaS can run all kinds of models. This includes behavioral and data models. As long as you have models and the matching solvers that can run in Linux OS, you are good to go in DTaaS. In some cases, models and solvers (tools) are bundled together to form monolithic DTs. The DTaaS does not limit you from running such DTs as well. DTaaS does not provide dedicated solvers. But if you can install a solver in your workspace, then you don't need the platform to provide one.

Does it support XML-based representation and ontology representation?

Currently No. We are looking for users needing this capability. If you have concrete requirements and an example, we can discuss a way of realizing it in DTaaS.

Communication Between Physical Twin and Digital Twin

How would you measure a physical entity like shape, size, weight, structure, chemical attributes etc. using DTaaS? Any specific technology used in this case?

The real measurements are done at physical twin which are then communicated to the digital twin. Any digital twin platform like DTaaS can only facilitate this communication of these measurements from physical twin. The DTaaS provides InfluxDB, RabbitMQ and Mosquitto services for this purpose. These three are probably most widely used services for digital twin communication. Having said that, DTaaS allows you to utilize other communication technologies and services hosted elsewhere on the Internet.

How a real-time data can be differed from static data and what is the procedure to identify dynamic data? Is there any UI or specific tool used here?

DTaaS can not understand the static or dynamic nature of data. It can facilitate storing names, units and any other text description of interesting quantities (weight of batter, voltage output etc). It can also store the data being sent by the physical twin. The distinction between static and dynamic data needs to be made by the user. Only metadata of the data can reveal such more information about the nature of data. A tool can probably help in very specific cases, but you need metadata. If there is a human being making this distinction, then the need for metadata goes down but does not completely go away. In some of the DT platforms supported by manufacturers, there is a tight integration between data and model. In this case, the tool itself is taking care of the metadata. The DTaaS is a generic platform which can support execution of digital twins. If a tool can be executed on a Linux desktop / commandline, the tool can be supported within DTaaS. The tool (ex. Matlab) itself can take care of the metadata requirements.

How can DTaaS control the physical entity? Which technologies it uses for controlling the physical world?

At a very abstract level, there is a communication from physical entity to digital entity and back to physical entity. How this communication should happen is decided by the person designing the digital entity. The DTaaS can provide communication services that can help you do this communication with relative ease. You can use InfluxDB, RabbitMQ and Mosquitto services hosted on DTaaS for two communication between digital and physical entities.

Data Management

Does DTaaS support data collection from different sources like hardware, software and network? Is there any user interface or any tracking instruments used for data collection?

The DTaaS provids InfluxDB, RabbitMQ, MQTT services. Both the physical twin and digital twin can utilize these protocols for communication. The IoT (time-series) data can be collected using InfluxDB and MQTT broker services. There is a user interface for InfluxDB which can be used to analyze the data collected. Users can also manually upload their data files into DTaaS.

Which transmission protocol does DTaaS allow?

InfluxDB, RabbitMQ, MQTT and anything else that can be used from Cloud service providers.

Does DTaaS support multisource information and combined multi sensor input data? Can it provide analysis and decision-supporting inferences?

You can store information from multiple sources. The existing InfluxDB services hosted on DTaaS already has a dedicated Influx / Flux query language for doing sensor fusion, analysis and inferences.

Which kinds of visualization technologies DTaaS can support (e.g. graphical, geometry, image, VR/AR representation)?

Graphical, geometric and images. If you need specific licensed software for the visualization, you will have to bring the license for it. DTaaS does not support AR/VR.

Can DTaaS collect data directly from sensors?

Yes

Is DTaaS able to transmit data to cloud in real time?

Yes

Platform Native Services on DTaaS Platform

Is DTaaS able to detect the anomalies about-to-fail components and prescribe solutions?

This is the job of a digital twin. If you have a ready to use digital twin that does the job, DTaaS allows others to use your solution.

Comparison with other DT Platforms

All the DT platforms seem to provide different features. Is there a comparison chart?

Here is a qualitative comparison of different DT integration platforms:

Legend: high performance (H), mid performance (M) and low performance (L)

DT Platforms	License	DT Development Process	Connectivity	Security	Processing power, performance and Scalability	Data Storage	Visualization	Modeling and Simulation
Microsoft Azure DT	Commercial Cloud	H	H	H	M	H	H	H
AWS IOT Greengrass	Open source commercial	H	H	H	M	H	H	H
Eclipse Ditto	Open source	M	H	M	H	H	L	L
Asset Administration Shell	Open source	H	H	L	H	M	L	M
PTC Thingworx	Commercial	H	H	H	H	H	M	M
GE Predix	Commercial	M	H	H	M	L	M	L
AU's DTaaS	Open source	H	H	L	L	M	M	M

Adopted by Tanusree Roy from Table 4 and 5 of the following paper.

Ref: Naseri, F., Gil, S., Barbu, C., Cetkin, E., Yarimca, G., Jensen, A. C., ... & Gomes, C. (2023). Digital twin of electric vehicle battery systems: Comprehensive review of the use cases, requirements, and platforms. Renewable and Sustainable Energy Reviews, 179, 113280.

All the comparisons between DT platforms seems so confusing. Why?

The fundamental confusion comes from the fact that different DT platforms (Azure DT, GE Predix) provide different kind of DT capabilities. You can run all kinds of models natively in GE Predix. In fact you can run models even next to (on) PTs using GE Predix. But you cannot natively do that in Azure DT service. You have to do the leg work of integrating with other Azure services or third-party services to get the kind of capabilities that GE Predix natively provides in one interface. The takeaway is that we pick horses for the courses.

Create Assets

Can DTaaS be used to create new DT assets?

The core feature of DTaaS software is to help users create DTs from assets already available in the library. Create Library Assets However, it is possible for users to take advantage of services available in their workspace to install asset authoring tools in their own workspace. These authoring tools can then be used to create and publish new assets. User workspaces are private and are not shared with other users. Thus any licensed software tools installed in their workspace is only available to them.

Does your platform adhere to GDPR compliance standards? If so, how?

The DTaaS software platform does not store any personal information of users. It only stores username to identify users and these usernames do not contain enough information to deduce the true identify of users.

Which security measures are deployed? How is data encrypted (if exists)?

The default installation requires a HTTPS terminating reverse proxy server from user to the DTaaS software installation. The administrators of DTaaS software can also install HTTPS certificates into the application. The codebase can generate HTTPS application and the users also have the option of installing their own certificates obtained from certification agencies such as LetsEncrypt.

What security measures does your cloud provider offer?

The current installation of DTaaS software runs on Aarhus University servers. The university network offers firewall access control to servers so that only permitted user groups have access to the network and physical access to the server.

How is user access controlled and authenticated?

There is a two-level authentication mechanism in place in each default installation of DTaaS. The first-level is HTTP basic authentication over secure HTTPS connection. The second-level is the OAuth PKCE authentication flow for each user. The OAuth authentication is provider by a Gitlab instance. The DTaaS does not store the account and authentication information of users.

Does you platform manage personal data? How is data classified and tagged based on the sensitivity? Who has access to the critical data?

The platform does not store personal data of users.

How are identities and roles managed within the platform?

There are two roles for users on the platform. One is the administrator and the other one is user. The user roles are managed by the administrator.