Digital Twin—Cyber Replica of Physical Things: Architecture, Applications and Future Research Directions
Round 1
Reviewer 1 Report
In this paper, the architecture, the applications and future research directions of a digital twin-cyber replica of physical things are presented.
The paper is well written and organized, only some improvements are required:
1. To highlight the importance of the topic, in the introduction section, more detail on the emerging practical applications of interconnected smart devices should be given, for example:
Smart farming
- M. K. Kazimierczuk et al., "Analysis and Design of Stand-Alone Photovoltaic System for precision agriculture network of sensors," 2020 IEEE International Conference on Environment and Electrical Engineering and 2020 IEEE Industrial and Commercial Power Systems Europe (EEEIC / I&CPS Europe), 2020, pp. 1-5, doi: 10.1109/EEEIC/ICPSEurope49358.2020.9160554.
Safeguard of Workers
- E. Pievanelli, A. Plesca, R. Stefanelli and D. Trinchero, "Dynamic wireless sensor networks for real time safeguard of workers exposed to physical agents in constructions sites," 2013 IEEE Topical Conference on Wireless Sensors and Sensor Networks (WiSNet), 2013, pp. 55-57, doi: 10.1109/WiSNet.2013.6488632.
Healthcare
- M. U. H. Al Rasyid, I. U. Nadhori, A. Sudarsono and R. Luberski, "Analysis of slotted and unslotted CSMA/CA Wireless Sensor Network for E-healthcare system," 2014 International Conference on Computer, Control, Informatics and Its Applications (IC3INA), 2014, pp. 53-57, doi: 10.1109/IC3INA.2014.7042600.
2. When the types of DT are explained in Section 2.2.2, more information related to possible applications and the advantages/disadvantages of each type should be included.
3. Please consider to summarized the characteristics of Data representation protocols and communications protocols in a table form.
Author Response
Dear Reviewer,
We would like to thank you very much for your efforts in processing and reviewing our submission!
Thanks
-Wei Yu
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The topics of Internet of Things and Cyber-Physical Systems fit the scope of the Journal. The manuscript requires extra efforts to improve its quality and presentation for the prestigious journal Future Internet. A set of comments are expounded hereafter.
- The manuscript is, in general, well organized and well written. However, there are some issues regarding the format of the document, as commented below.
Figures should be placed after the text that comments them.
Figure captions and titles of tables lack the terminal period (punctuation).
Sections like Authors contributions, conflicts of interest, etc. are missing.
Concerning the references, the format must be slightly revised to follow the template concerning some aspects like the abbreviated name of the journals, etc.
- About the content of the manuscript, it covers a very interesting topic. The comments after a careful revision are the following:
The type of paper should be considered as Review instead of Article.
In the same sense, due to the review task performed in the research, certain information about the search procedure and criteria should be added to the manuscript. In other words, the methodology followed to search and filter papers must be commented, at least, in a brief manner. What are the search terms? What are the scientific databases where the papers have been found? This information must be provided when a high-quality review paper is written.
In subsection 2.4, Communication Protocols, the well-known Modbus TCP/IP has not been included. In this regard, this reviewer suggests including it at least in a brief manner given the fact that it is widely applied in industrial and energy context, including smart grids and microgrids. The following recent papers could be considered by the authors in order to support the new text:
- Innovative multi-layered architecture for heterogeneous automation and monitoring systems: Application case of a photovoltaic smart microgrid, Sustainability, 13 (2021) 1–24. https://doi.org/10.3390/su13042234.
- Microgrids: Overview and guidelines for practical implementations and operation. Applied Energy 2020, https://doi.org/10.1016/j.apenergy.2019.114039
Indeed, it has been pointed as a protocol in the IoT framework by some recent work in the journal Future Internet:
- Communication protocols of an industrial internet of things environment: A comparative study, Future Internet. 11 (2019). https://doi.org/10.3390/fi11030066.
In the third section, including a graph to show the analyzed publications over years would illustrate the increasing interest in digital twins and IoT. Alternatively, some “cheese style” chart could be used to depict the papers devoted to the covered topics (smart grids, smart manufacturing, smart cities, etc.).
The role of open source technology could be commented given the importance that this technology is acquiring for paradigms, digital twins and IoT. For example, some recent work in this regard can be found in:
- Real-Time Implementation of a Fully Automated Industrial System Based on IR 4.0 Concept. Actuators 2021, https://doi.org/10.3390/act10120318
- Low-Cost, Open Source IoT-Based SCADA System Design Using Thinger.IO and ESP32 Thing. Electronics 2019, 8, 822, doi:10.3390/electronics8080822.
Commenting cyber-security issues, section 5.4, is a positive feature of the paper.
The term “cyber replica” is very interesting but it only appears in the title of the manuscript. It is suggested to include such a term in some text within the paper, at least in the Final remarks section.
Author Response
Dear Reviewer,
We would like to thank you very much for your efforts in processing and reviewing our submission!
Thanks
-Wei Yu
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The concerns of the Reviewers have been properly addressed in the new version of the manuscript. Therefore, the paper has been enhanced and is a valuable review contribution in the scope of digital twins. Congratulations to the authors for their efforts.
