Review of "OpenCitations Meta"

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This paper introduces OpenCitations Meta, an important new component in the open infrastructure that is being created by the team of OpenCitations. I see OpenCitations Meta as a crucial milestone in the development of this infrastructure. The paper is generally well written and offers a lot of useful information about OpenCitations Meta. I have a few relatively minor suggestions for improvements.

The paper uses quite some Semantic Web terminology. Some parts of the paper may be difficult to understand for readers who are not familiar with this terminology. In the introduction of the paper, my suggestion would be to refer these readers to sources they can use to familiarize themselves with Semantic Web ideas and the related terminology.

I believe the most important weakness of the paper is the way in which the authors present the benefits of OpenCitations Meta. In the introduction and conclusion sections, and also in the abstract, the authors discuss three benefits of OpenCitations Meta. These are benefits relative to the infrastructure that was provided by OpenCitations before the release of OpenCitations Meta. While it is understandable that this is a natural perspective for the authors, I don’t think this perspective is particularly appealing to the typical reader. I expect readers to be interested in the benefits of OpenCitations Meta relative to other open and closed infrastructures. For most readers this will be much more important than the benefits of OpenCitations Meta relative to the OpenCitations infrastructure before the release of OpenCitations Meta. My suggestion to the authors therefore is to rewrite the introduction and conclusion sections of the paper in a more user-centric style (rather than the current style that is more developer-centric).

Two small issues:

1. I don’t fully understand the idea of supplier prefixes in OMID identifiers, as discussed in Section 3.1. The authors state that “060 corresponds to the supplier prefix, which indicates the database to which the bibliographic resource belongs (in this case, OpenCitations Meta)”. Does this mean that all entities in OpenCitations Meta have the supplier prefix 060? If the prefix is always the same, why then do we need the prefix? It seems redundant. Also, it is not clear to me why the prefix starts with ‘06’. Why not ‘01’, for instance? I also don’t understand why the prefix must have a ‘0’ at the end. Some further explanation would be helpful.

2. The numbers reported in the first paragraph of Section 4 are important. My suggestion therefore is not to report these numbers in the text, but to present them in a table.

Full disclosure: I am chair of the advisory board of OpenCitations.