Semantic Web and its Role in Facilitating ICT Data Sharing for the Circular Economy: An Ontology Survey

First of all, I'd like to acknowledge that the authors did a substantial effort to revise the paper,
resulting in a much higher quality, so thanks for that.
However, some more clarity on the specific scope of the work should be given (it is already better by excluding the standards):
it now feels as if this paper presents an ontology survey on the ICT domain for CE, but it is rather an _academic_ ontology survey and evaluation on existing ICT (focussing on laptops), material, and CE ontologies. This scope is currently not wel represented making the paper feel as if it overpromises.
For me, an accurate scoping and limitations discussion must be added to the paper before I can accept it.

One note on my emphasis on 'academic' above: a potential identified risk in the presented survey methodology is solely relying on academic sources that contain paper publications. A quick search on ontology portals such as Linked Open Vocabularies (https://lov.linkeddata.es/dataset/lov/terms?q=usb) reveiled http://www.ebusiness-unibw.org/ontologies/opdm/computer.html : a (well-published) ontology that covers many of the laptop competency questions (whereas now the paper gives the impression this is a large hole to be filled). By better scoping the paper and discussing its limitations, its research value would increase.

Some more detailed comments below

- For me, the rephrased paragraph on p3 lines 6-29 doesn't sufficiently resolve the comment that this paragraph is describing multiple arguments without a clear structure. I re-iterate that I think this section would be much clearer if you start with an overview paragraph and then go into details, so first "[...] adoption of the CE [...] is currently limited due to (i) siloed knowledge about the CE and ICT resulting in lack of transparency and traceability of ICT procurement, and (ii) data findability, accessibility, and interpretation. This can also be seen as a result of the CE standardisation still being under development. There is yet no single CE standard to be used as a main reference point across the European Union (EU) thus there is a lack of a unified terminology for CE’s processes and guidelines/best practices for implementing the CE across different sectors". and then 2 paragraphs to each give the details of (i) and (ii), respectively.
- Although it is true that "The main use case of our work has been clearly stated in the introduction of the paper (page 4 line 43)", it can be made more clear as to _why_ you focus on laptops. Some argumentation is found throughout the introduction, but laptops are always given as an example among, e.g., tablets, which makes it unclear for the user that this will be a focus point. I suggest to introduce the focus and its need early-on (and have its argumentation condensed in the beginning, i.e. its short lifetime compared to its increasing use) condensed in one paragraph to make this very clear. And clearly state this in the abstract.
- The original question of the reviewer "Is this survey even applicable to the whole ICT domain then? Why/why not?" is not addressed nor in the response letter nor in the paper. Maybe it's important to clarify this by slightly altering the title to 'A Focused Ontology Survey'. Although I think you can generalize your discussion points of Section 6 beyond laptops, the actual competency questions etc. are focused on laptops and not straightforwardly applicable to the larger ICT domain. It would be interesting to discuss how this work could be reused for another focus point (within the ICT domain), e.g. what is needed to refocus this work from 'laptop' to 'smartphone'?
- I appreciate the fact that you removed the PRISMA reference if you indeed did not follow it, however, in your original submission you explicitly state "we followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) [41] methodology". This is very contradictory and damages your research integrity. I would strongly advise to be careful making such (false?) statements in the future.
- p5 l37: shouldn't this be BSI instead of BIS? Also the footnote for BSI contains some rogue latex code.
- Is the mentioning of the standardisation bodies still relevant given you no longer include the standardization overview?
- I commend the authors for extending tables 2-4. Much clearer (and in my opinion, much more valuable) now.
- For me, the 4.2 intro sentence "This subsection presents an overview of semantic models for materials motivated by the the existing work that was reviewed in [72]" does not clarify enough that this work was used "as a starting point for our survey".
- I don't have the feeling the question about cost and stock competency questions is correctly answered, I understand the use of knowing such properties, but I don't think the authors address the original question "do you expect that this type of data actually accurately exists, knowing that, e.g. different factories could employ very different pricing strategies?"
- similar for the next question, the reviewer's question is about 'can you get this data without scoping it to a specific context'?
- I'd like to see clarified in Section 5 _how_ each ontology was investigated, as some results are questionable. For example, 'dogont:Device' is not a concept that exists. 'ssn:Device' is referenced in the ontology file, but it's not actually used as part of the ontology. Clarify how you performed the analysis: was this a one-person job, was this reviewed by other experts, was this automatically done by querying the ontology on keywords, ...?
- In Table 8 I would clarify which key concepts are the descriptions and which are examples (the confusion arises as only some competency questions such as Q8, Q30, Q31 have examples, maybe better to move the examples to the competency questions? "What type of battery is used? (e.g. alkaline, NiCad, Li-Ion)"

The paper is a revised version of an earlier submission, considering most of the comments by the reviewers. Given that, the manuscript has considerably improved since the last submission. As a survey article, the paper is suitable as an introductory text, but the scope of the survey (ontologies for CE of ICT devices) is very narrow, and the content will not be interesting to a large part of the journal's audience. Nevertheless, it shows the complexity of the CE domain, and the need for combining ontologies in many fields, which is a useful observation in itself.

The main weakness of the paper is still the methodology, and consequently the comprehensiveness and reliability of the survey results. Although the methodology description has been improved, I still find it quite vague and not well described. On one hand the methodology applied is extensive, i.e. with many steps, but most of the steps are actually quite unrelated to the survey itself, but rather explains the context of the survey, e.g. how requirements were elicited, and how a decision was made to focus on a certain typ of device. While the steps really relevant for the survey part (4 and 5), and the paper, are glossed over, but saying that a set of keywords were submitted to a set of databases. However, I am missin the information about how many hits were returned, how these were first scanned, what inclusion and exclusion criteria were applied, and in what order etc. How many people were involved in the assessment etc. Based on this lack of information it is not clear how reliable the survey is, and if it is comprehensive and unbiased (e.g. with respect to already known work).

I also still strongly suggest that the authors clean up the use of terminology, such as "expressivity" and "expressiveness", which is sometimes used to indicate the level of detail or granularity of modelling, and sometimes refers to language expressivity. For instance, in my opinion it is not correctly used in sections 4.1.6, 4.1.7, 4.1.10. In section 4.1.11 comes an attempt to define the term, but this is too late, and I would rather refrain from using the term rather than redefining its meaning.

I am also quite puzzled by section 4.4, which is supposed to present applications of ontologies - as opposed to papers merely presenting ontologies, in the previous subsections. However, in many of the earlier papers there are also applications presented, and the papers listed under 4.4 seem to also present ontologies - so what is the criteria for this category actually? Why are these ontologies not included in the previous sections? Or the other way around: all applications, also from previously listed papers, presented in this section?

At the end of section 1, ontologies are suddenly called "semantic models", this terms should be introduced explicitly before used here. I assume this is a more generic term, encompassing also what is later called taxonomies and schemas?

Figure 2: The box below step 2 does not really seem to be a task.

Section 3: I think "computational ICT properties" deserves a more detailed definition in the paper. The authors explain it more in the response letter, but it should be in the paper.

Figure 3: what is the notation used here? What do the arrows mean?

In section 4 I would suggest to refrain from repeating any statements by the referenced papers that are not clearly factual. I have not read the paper of 4.1.1, but "scalable framework" is a claim that should be supported by some evidence or a discussion, but is now simply stated in the text.

There are still some occurrences of development tools mentioned in the text, although the authors said they had been removed. For instance this appears in 4.1.4, 4.1.9, 4.2.11

The acronym OWL is introduced in 4.1.7, while it has already been used many times before that.

Some detailed comments and issues:

Throughout the paper, semantic web technologies is used almost as a synonym for ontologies, which I do not agree with. There are many other technologies and standards, in addition to ontologies, that make up the semantic web. Especially in the title of section 4.4 ontologies should be mentioned specifically, and not Semantic Web in general.

I do not really agree with the sentence at the end of page 11 and beginning of page 12, about OWL 2. Since OWL2 is an extension of OWL (1) then if you have an ontology in the previous version of OWL, it is also in OWL2, as far as I remember nothing was removed, i.e. no breaking changes. And OWL 2 was introduced in 2012, so any OWL ontology developed after 2012 (which includes most of the ontologies mentioned in the paper) are bound to be OWL2 compatible, most certainly if it has been created with an OWL 2 compatible tool, e.g. Protégé. So I don't think this is an issue that even needs to be mentioned, unless you start to really investigate the expressivity and OWL profile of the ontologies, which is not the case in the paper. I would also suggest to remove OWL2 and OWL2 DL in Table 3 and simply write OWL in that column, and change the last sentence of 6.2.

The last sentence of 4.2.8 is ambiguous, what is it that is not available online?

As far as I am aware, the ontologies in 4.3.3 are no longer available online, and no longer maintained, hence certainly not under development. This is also repeated in 4.3.5. On a general note: I have not double checked this, but I assume that the authors have actually double checked the availability of all the ontologies claimed to be freely available? Since these problems could otherwise also hold for other ontologies surveyed.

Section 4.3.4, second to last sentence contains a footnote to Excel, which is quite common knowledge, while the second tool has a strangely formulated name (in parenthesis).

What do you mean with "missing domain and range of classes" in the last sentence of page 19? Do you mean properties?

Language issues:
- Abstract: build -> built
- Bottom of page 2: either "results are" or "result is"
- Missing reference and a strange sentence in the last row, application column, of Table 2.
- Section 4.2.2: represented -> represent
- Section 4.2.4: metalic -> metallic, evaluate -> evaluated
- Section 4.2.7: knwoledge -> knowledge
- Section 4.2.9: is has -> has
- Section 6.1: The reuse of specific ontology -> The reuse of a specific ontology, and "ontology's availability" -> "an ontology's availability". Strange word order in the second to last sentence.

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