Semantic Node-RED for Rapid Development of Interoperable Industrial IoT Applications

Tracking #: 2180-3393

Aparna Saisree Thuluva
Darko Anicic
Sebastian Rudolph
Malintha Adikari

Responsible editor: 
Guest Editors SemWeb of Things for Industry 4.0 - 2019

Submission type: 
Full Paper
The evolution of IoT has revolutionized industrial automation. Industrial devices at every level such as field devices, control devices, enterprise level devices etc., are connected to the Internet, where they can be accessed easily. It has significantly changed the way applications are developed on the industrial automation systems. It led to the paradigm shift where novel IoT application development tools such as Node-RED can be used to develop complex industrial applications as IoT orchestrations. However, in the current state, these applications are bound strictly to devices from specific vendors and ecosystems. They cannot be re-used with devices from other vendors and platforms, since the applications are not semantically interoperable. For this purpose, it is desirable to use platform-independent, vendor-neutral application templates for common automation tasks. However, in the current state in Node-RED such reusable and interoperable application templates cannot be developed. The interoperability problem at the data level can be addressed in IoT, using Semantic Web (SW) technologies. However, for an industrial engineer or an IoT application developer, SW technologies are not very easy to use. In order to enable efficient use of SW technologies to create interoperable IoT applications, novel IoT tools are required. For this purpose, in this paper we propose a novel semantic extension to the widely used Node-RED tool by introducing semantic definitions such as semantic models into Node-RED. The tool guides a non-expert in semantic technologies such as a device vendor, a machine builder to configure the semantics of a device consistently. Moreover, it also enables an engineer, IoT application developer to design and develop semantically interoperable IoT applications with minimal effort. Our approach accelerates the application development process by introducing novel semantic application templates called Recipes in Node-RED. Using Recipes, complex application development tasks such as skill matching between Recipes and existing things can be automated.We will present the approach to perform automated skill matching on the Cloud or on the Edge of an automation system. We performed quantitative and qualitative evaluation of our approach to test the feasibility and scalability of the approach in real world scenarios. The results of the evaluation are presented and discussed in the paper.
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Review #1
By Raghava Mutharaju submitted on 01/Jun/2019
Major Revision
Review Comment:

This paper describes the semantic extensions to an IoT application development tool called Node-RED. Semantic application templates called Recipes are used for matching the skills or the capabilities of things with the application requirements. Models from are used to semantically enrich the nodes from Node-RED. W3C WoT Things Description (TD) are generated automatically from the iotschema nodes of Node-RED. These TDs are stored in the form of a Knowledge Graph either centrally on the Cloud or distributed across the Edge devices. Experiments were conducted using both these approaches and results were discussed.

I have the following concerns with the papers

1) I think this should be an "Application Report" rather than a full paper. I am not sure what the research contributions are. It is not clear from the paper and neither are they specified explicitly. It is a very nice application of Semantic Web technologies in solving problems in the IoT space. But beyond the standard modeling and querying techniques, I fail to see what the research contributions are.
2) The following information is spread across the paper and is not completely clear - what are the specific additions and work that is different in the journal submission as compared to the authors' earlier publications? Please put this information in the Introduction section (towards the end perhaps) and mention clearly what the add-ons are.
3) What parts of the entire workflow (for example from Figure 1) are automated and which of them are not? It looks like only the matchmaking part is automated.

Other questions/comments

a) When explaining the approach in Sections 4, 5, 6, and 7, it will be good if authors can map it back to the development steps from Figure 1.
b) The recipe flows and matchmaking in Node-RED seem related to Semantic Web service composition and discovery. Please include relevant papers in the related work and comment on how this work compares to the composition and discovery work from the past.
c) The term semantic reasoning has been sprinkled across the paper but it is neither explained nor clear how reasoning is used and what reasoner is used (is it VLog?).
d) The details of matchmaking are not clear. From Section 7.2, how is Recipe Flow converted to SPARQL queries? How do SPARQL queries help in matchmaking? Is matchmaking always a binary case (match or no match) or will be there cases of "closest" match? For the use case in the paper, mention how SPARQL queries are generated and also put the queries in the paper.
e) The phrase rapid application development has been used throughout the paper but the term "rapid" has not been defined or quantified by the authors. How rapid is rapid? As part of the user studies I was expecting the following - time taken by the users before and after the semantic extensions to Node-RED. This is missing and the authors claim this to be the key selling point of their work.
f) How does the TD Generator semantically enrich TDs from iotschema nodes (Section 6.1)?
g) Did you try the standard triple stores on Edge devices? How was that experience (performance, memory usage etc.)? Putting these things in the paper would serve as a better motivation for choosing VLog.
h) Since the VLog store is distributed across the Edge devices (Section 7.2.2), how much of a communication overhead will there be while loading TDs and querying them? Do you meant "replicated" instead of "distributed", i.e., all the TDs are replicated on all the Edge devices (and not distributed across them). If it is distributed then my question on communication overhead holds. If it is not, then the terminology used in the paper has to be changed.
i) Page 23, Q1, common practice is mentioned here but it would be helpful if the common practice was discussed early in the paper (so that the readers can appreciate what the difficulties in using non-semantic Node-RED are).
j) Page 8, the format of text on the left side is different (line spacing is more?) from rest of the paper.
k) The quality of some of the figures is not good - Fig 3, 4, 5, 6 for example.
l) Fig 5 needs a legend for the different colors used.
m) Section 5, what are brown-field and green-field things?
n) Section 5, can new adaptation nodes be created by the users?
o) Page 22, under "User Evaluation with Siemens Engineers", the sentence "... user evaluation of the tool with Siemens expert engineers (who are non-experts)." is not clear. Who are the experts (and in what) and who are the non-experts (and what are they non-experts in)?

Spelling/Bibliography/Grammar corrections

i) Page 1, it should be digitize and digitization rather than digitalize and digitalization.
ii) Page 2, "... and expensive. As the state of the art IAS and BAS are engineered ...". Starting with As is not correct and is abrupt - there is not continuation from the previous sentence. This needs to be rewritten.
iii) Page 7, in the sentence "... maximum one input and one ore more ...", it should be or and not ore.
iv) Page 23, summary is misspelled as summery.
v) Some of the references are missing year and/or pages. Reference 28 has weird characters in it.
vi) Page 22, it should be "On" instead of "At" in the sentence "At this occasion, ...".

Overall, this work is a very good demonstration of how Semantic Web technologies can play a key role in making IoT application development better and easy. However, as mentioned above, the research contributions and some parts of the paper are not clear.

Review #2
Anonymous submitted on 04/Aug/2019
Minor Revision
Review Comment:

This paper underpins a very interesting problem of interoperability of heterogeneous IoT devices. The heterogeneity of IoT devices is continuously posing challenges to the application development and absence of any such solution clearly demonstrate the significance of efforts presented in this paper.

This paper investigates the possibility of using semantic web technologies to achieve semantic interoperability of IoT devices. Authors claim that this will enable non-experts to develop applications. Authors also claim that the proposed approach accelerates the application development process by introducing novel semantic application templates called Recipes in Node-RED as Node-Red is most commonly used tool for IoT application development.

The proposed approach is well analysed and very well explained. The paper also presents a detailed evaluation of the proposed approach. However, the details of the development and how non-expert application developer will be able to develop an application for heterogeneous devices is not very clear. Some more clarity in this respect will assist readers to appreciate the efforts made by the author.

In general the paper is well written.

Review #3
Anonymous submitted on 12/Sep/2019
Minor Revision
Review Comment:

In this paper, the authors proposes a novel semantic extension to the widely used NodeRED tool by introducing semantic definitions into NodeRED. The used semantic definition is
The authors present the approach to perform automated skill matching on the cloud/edge of an autonomous system. The authors performed quantitative and qualitative evaluation to test the feasibility and scalability of the approach in realword.

The paper is well structured and easy to follow. The followings are some suggestions, which may help the authors:
- The authors may present the limitations of the proposed method. NodeRED is an excellent tool for rapid IoT/IIoT development tool. It reduces the application development and prototyping. However, there may be some limitations associated with the NodeRED and so, the proposed method as well. It is a request to include the limitation of the proposed method with NodeRED.

- The authors may present their experience regarding the deployment of this tool in the real production environment. The use of Siemens factory case study would make this paper more interesting and relevant.

- The scope of the paper and basic assumptions in Introduction section are recommended.

- It is my recommendation to expand the future work of this paper. How this interesting work would be useful for the next work.

- The quantitative and qualitative evaluations may have some bias. It is my recommendation to describe the test scenarios and their basic assumptions, threat to validity and tools used during the evaluation study.