Cluedo4KG: clues for learning SW technologies

This paper presents two tutorials designed to practice how to write queries in SPARQL and how to create/edit ontologies in OWL. These two tutorials are designed based on the famous board game Cluedo, in which players need to find a murderer at a crime scene. In the tutorial on SPARQL, students need to write SPARQL queries to get information about the crime scene step by step to find who the murderer is. In the second tutorial of OWL, students need to construct the ontology of the crime scene step by step. These two tutorials were evaluated in a classroom setting. Students were mostly satisfied with the tutorials. The authors have open-sourced these tutorials on GitLab and also made available the KG on w3id.

Overall, I find the tutorials quite interesting and fun to play with. I think these resources are valuable to share with the community. I can see these tutorials easily adopted in other Semantic Web courses. My comments below are mainly about the presentation.

First, it would be helpful to include some screenshots of the web interface. It wasn't quite straightforward to me how students played the game by writing SPARQL queries until I saw the first question in the SPARQL tutorial.

Second, I would make it more clear and explicit at the beginning of the paper that these tutorials are for practicing the use of SPARQL and OWL. These tutorials are not designed to teach the SPARQL or OWL concepts, features, etc. Since this paper emphasizes a lot on "learning", I initially thought these tutorials would include some descriptions of SPARQL and some code examples.

Third, Table 1 and Table 4 are hard to read since there are no borders, and the cells do not seem to be aligned. The authors should improve the presentation of these two tables.

The link in Footnote 18 doesn't work.

The paper is mostly well written and give a concise description of the provided resources, which consist of a number of didactic datasets together with a web application. All resources are easily available.
There are some minor comments and hints for improvement:
- the terms ontology and knowledge graph are used interchangeably without explanation, this might be a bit confusing;
- the initial ontology misses a version information, the issue date is in 2012, information about maintenance is not given;
- initially no established vocabulary are used, all basic classes are modeled as proprietary classes - this is mentioned in the paper, but not explained;
- the resources are repeatedly used in the authors courses on Semantic Web Technologies at Master's level, third party uses are not mentioned;
- there is an inconsistency in prefixes used in the (extract of the) ontology and the SPARQL query compartment; the authors state to have done this deliberately to focus on IRI management; nevertheless, there could have been a hint in the application;
- the paper text has some minor typos: p. 2, l. 46 triples (not: triple); p. 4, l. 47 skills (not: skilled), p. 5, l. 6 named (not: name), p. 6, l. 40 all the (not: the all), p. 8, l. 4 two (not: too), p. 8, l. 18 result (not: resul).
Finally: I couldn't reproduce the count of object property and data property assertions in Cluedo4KG. According to my estimate, there are significantly more.

The paper describes an approach to teach semantic web technologies (SPARQL and OWL) based on the Cluedo game. The approach consists of asking questions to the students using some existing data and ontology about the crime scene. The paper indicates that the authors have used it in their course with some successful adoption.

Overall, I think the approach is nice and I think it can help the motivation of the students. Proposing a simple domain with 4 classes and not a lot of instance data can be helpful to identify mistakes in the queries proposed by the students.

Although the paper is submitted as a data description, I think it is not really a data description but I also think there is probably not a category that fits better, because it is also not a research paper, so I assume, it is OK to present the paper in this category.

In general, I think the materials presented by the authors are valuable and as a teacher of semantic technologies I would even like to use the tutorial materials in my course. So I really encourage the authors to keep working on it.

Some minor comments:
- The list of references is very short and I have the feeling that the authors are missing other books and materials that can be used to teach semantic technologies. At least, 2 books that I use in my teaching (disclaimer, I am a coauthor of them are: [1] and [2]), but there are other books like [3] which are very useful for teaching semantic web technologies. would recommend the authors to extend a little bit the references about related teaching material.
- Page 2. SPARQL 1.1 <> OWL
- Page 2. Last sentence contains “kn-woledge”
- Page 3. knowledge graph accessible through <<à/a>> SPARQL
- Page 4, section 2.2.3, starts with a simple sentence “The tutorial must be run from the Web application.” followed by a dot and a newline which is a bit ugly…I would recommend not to create a newline after that dot or extend a little bit the sentence.
- Page 4. Table 1 details in which step the various targeted <> are addressed
- The evaluation part contains numbers which are a bit vague like “around 90% of students…”, I think it would be better if the authors could provide the raw numbers of how many students completed the course as well as how many students were enrolled in the course and their background. Are those numbers about some specific course (maybe last year?) or about all the courses that the authors have used the tutorial.
- Page 6. I think “softwares” in plural is wrong.
- Page 6. “Assuming <> all entities use the same namespace
- The authors employ RML to convert CSV files to RDF. Maybe the authors could take into account other approaches like ShExML which were created to have better usability [4] (disclaimer: I am a coauthor of that paper, I am not mandating the authors to cite it, just indicating that they could extend a little bit the references or consider other technologies). I think the authors could add a “Related work” section to the paper to extend those references.
- Page 7. I think the sentence “and another possible solution will likely a different though similar amount of entities and triples.” needs a verb and probably the first could be removed.
- Page 7 add a dot and a space in “step instructionsAlternatively”
- Page 8 “...were <> disjoint classes
- Page 8. <>
- Page 8. <>
- Page 8. Add a space after dot in “file.Alternatively”
- Page 8. “Targeted <>”
- Page 8 “two axes : “ (remove the first space)
- Page 9. Table 4 is a bit difficult to read as it is very sparse…maybe adding some lines could help its readability.
- Page 9. A verb is needed in “and might further the student’s understanding of the open world assumption”
- Page 10. “60 M2 students”, what are M2 students?
- Page 10, “softwares” should be without plural
- Page 10. “to go more in depth in of how” is strange?
- Page 10. “The resources used for the application are available under an open licence and published in accordance with semantic web best practice.” I don’t think the semantic web best practice is about publishing with open licence…If the authors wanted to follow semantic web best practices, maybe the tutorial materials should be published with more metadata in a web page.
- Page 10. “A tutorial for <> SHACL.”
- I tried the system using the English version and I found that some of the URIs are using descriptive names with names in French which would probably require some adaptation. To solve that, I would probably replace the descriptive URIs by opaque ones [5] which would facilitate its adoption in other languages.
- When I tried the system, I found it a bit too constrained to have to provide two names of people to use it. I wonder if it could be more flexible and allow one or more names of students. It is also not clear what the system is doing with the introduced names…is it storing the results in some place?
- I also think the system is not storing the interaction results of the students in any kind of database. If it isn’t , I suppose that it could be a feature that the authors could consider for future work? In fact, although the approach is nice, I think it would be great if it could also help the students improving the feedback they obtain or the teachers sending some performance results from the students.
- In the SPARQLuedo system, the color used to present the results (white) on top of the yellow box makes them very difficult to see…I asked a colleague and we both have the same problems with the lack of contrast in the colors. I wonder if the students in the course didn’t complain about it because it makes it difficult to read the results of the SPARQL query.

[1] Jose E. Labra Gayo, Eric Prud’hommeaux, Iovka Boneva, Dimitris Kontokostas (2018) Validating RDF Data, Synthesis Lectures on the Semantic Web: Theory and Technology, Vol. 7, No. 1, 1-328, DOI: 10.2200/S00786ED1V01Y201707WBE016, Morgan & Claypool
[2] Aidan Hogan, Eva Blomqvist, Michael Cochez, Claudia d’Amato, Gerard de Melo, Claudio Gutierrez, Sabrina Kirrane, José Emilio Labra Gayo, Roberto Navigli, Sebastian Neumaier, Axel-Cyrille Ngonga Ngomo, Axel Polleres, Sabbir M. Rashid, Anisa Rula, Lukas Schmelzeisen, Juan Sequeda, Steffen Staab, Antoine Zimmermann (2021) Knowledge Graphs, Synthesis Lectures on Data, Semantics, and Knowledge, No. 22, 1–237, DOI: 10.2200/S01125ED1V01Y202109DSK022, Springer.
[3] Aidan Hogan. "The Web of Data". ISBN:9783030515805, Springer Nature, October 2020.
[4] ShExML: Improving the usability of heterogeneous data mapping languages for first-time users, Herminio García-González, Iovka Boneva, Sławek Staworko, José Emilio Labra-Gayo, Juan Manuel Cueva Lovelle, PeerJ Computer Science, 2020
[5] Labra Gayo, Jose Emilio, Kontokostas, Dimitris, and Auer, Sören. ‘Multilingual Linked Data Patterns’. 1 Jan. 2015 : 319 – 337.