Review Comment:
The article surveys contributions of the semantic web to the internet of things. Authors propose a model, LMU-N to classify the contributions and analyse the current trends. LMU-N is a graph model, where nodes (partitioned in lower, medium and upper nodes) are connected through message flows. The article is clearly on topic with the special issue, and surveys are usually welcome to let interested researcher get started with the topic.
My main critical points are related to the survey methodology.
First, the selection of the articles. Authors state that they found 1426 publications and that they focused on 71. Authors explain that they selected the papers based on "their quality, their innovative aspect and for the balance in their content between semantic web and IoT". It is very hard to understand how they measured these values. For example, how do the authors judge the quality of the paper? The methodology deserves a more depth explanation in the paper. As an example, this article contains a proper explanation of the methodology: Kitchenham et al., "Systematic literature reviews in software engineering – A systematic literature review", Information and Software Technology, 51(1), but it is very easy to find other papers following similar structures. In my opinion, the selection of the articles is one of the most important parts of this article, since most of the findings are related to this set. For instance, Section 3.1.1 states: "The importance of the enrichment process is underlined by the important number of publications contributing to it: 17 papers in this survey", and Section 3.2 reports: "Discovery is a widely implemented process (10 contributions in this survey)". Without a clear explanation about how the papers were selected, it is hard to accept these results.
Second, the model used to classify the contributions. Authors state that LMU-N covers at least partially 72% of the articles, and situates precisely 53% of the articles. The fact that 28% of the articles do not fit can be explained by the fact that articles on semantic web and IoT have a slightly different focus. In my opinion, this suggests that LMU-N is not a model to capture semantic web contributions to IoT, but it captures something more specific, e.g. semantic web contributions to IoT architectures. However, if this was the scope of the paper, the first part should be reviewed to refine the scope, and the search methodology should be revised as well.
The paper is also very hard to read. There is a huge number of typos, which make hard to focus on the content. Moreover, there are several repetitions that lead on the overall readability of the article.
I report below some detailed comments.
Abstract
--------
1.1: "The diversity of these application domains is the source of the very high technological heterogeneity in the IoT": is it really the cause? There are a lot of heterogeneity problems also in the same application domains, given by the different types of "things" involved, the different goals, the different protocols.
Section 2
--------
2.1: Section 2.1 sounds more as "Method" than "Motivations".
2.2: What are those architectures that you considered to build LMU-N? You should at least cite them in Section 2.2
2.3: In Sec 2.2 you present the DIKW pyramid, but you do not discuss W (wisdom) at all. What is the reason behind this choice?
2.4: How does Section 2.3.3 (Ontologies for the SWoT) relate to Section 2.3 (Using LMN-U to classify SWoT contributions)?
2.5: It is very unusual to write a whole section (Sec. 2.4) as a pointed list. You may just remove them and use paragraphs instead
Section 3
---------
3.1: Enrichment: as written above, the 17 papers covering this point is not a strong claim. The same holds for the 47% of articles that cannot be situated precisely into LMU-N
3.2: Lowering: while I agree on the importance of this action, I am not very sure that it implies moving downward in the DIKW pyramid. A system that gains the knowledge to decide actions is not losing such knowledge when lowers the action for the actuator.
3.3: What is the relation between control and lowering (w.r.t. LMU-N)? They seem to largely overlap.
3.4: Why is Querying described in "Transport" and not in "Processing content"? Querying is a type of processing, isn't it?
3.5: I disagree on the fact that Aggregation produces "new content instance of the same level in the DIKW hierarchy". Actually, aggregation is one of the most classical ways to move up in this pyramid. We can consider for example censuses, where aggregations over population data create information and knowledge. Moreover, the term aggregation referred to data, information and knowledge usually assume different meanings.
3.6: You state that consistency is not a topic limited to the SWoT, but it looks to me that the same argument holds for most of the points you discuss in Section 3. I agree that "generic consistency mechanisms could be applied to IoT datasets", but the interesting question, in my opinion, should be related to which peculiarities of the IoT domain can be exploited to let such mechanisms perform better in this specific scenario.
3.7: I do not understand what is the point of the last paragraph of Decision Support
3.8: Why did you choose to name two processes of your model with the same name, i.e. Abstraction in Sections 3.1.3 and 3.2.2? It is a bit confusing.
3.9: The identified trends follow are an outcome of the selection of the articles. This section would benefit from a more detailed description of the selection process, as motivated above.
Section 4
---------
4.1: Sec. 4 states: "semantic web contributes to the emergence of the SWoT, but semantic web technologies and principles must also be adapted to meet the constraints of the IoT in order to develop the SWoT". It is not clear to me how these two facts indicate that contributions between semantic web and IoT are not unidirectional. It happens very often that adaptations are required to apply some technologies in some specific domain. As a consequence, it is not evident to me the difference between the contributions described in Sections 3 and 4.
Section 5
----------
5.1: What does "the use of decentralized approaches to LMU-N processes is also crucial to scalability" mean?
5.2: What is the goal of the last four paragraphs of the paper (last paragraph at page 20, paragraphs at page 21)? It is not clear if they are final remarks or future work. Maybe it can be better framed.
The text is full of typos, and a proper revision is required. For example:
- UN (LN, MN) is used in both singular and plural form. A possible solution is to use UN (LN, MN) as singular name, and UNs (LNs, MNs) as plural one.
- All the articles in the bibliography have the title ending with comma followed by double quote, but it should be the opposite (double quote followed by comma)
I report the ones I found in the introduction (the list is too long to report all of them):
deployment of devices and services networks -> deployment of device and service networks
Dublin (IR) -> Dublin (IE)
(JA), that are -> (JA), which are
to monitor their environment -> to monitor their environments
”Things” -> “Things”
2009[3] -> 2009 [3]
manufacturing... -> it is a bit informal to use "..." and "etc.", so they should be avoided in scientific articles. A possible way to rephrase is: "by the IoT, such as environmental metering, [...], and manufacturing."
an application developers should -> "an application developer should" or "application developers should"
diversity[7] -> diversity [7]
feed the Linked Open Data (LOD) -> feed the Linked Open Data (LOD) cloud/project
section 2 defines -> Section 2 defines
On the other hand, section 4 -> when you use "on the other hand", there should be "on the one hand" before
|