The citation graph is not too valuable unless you also have the context and reason for the citation
I totally agree with this, and I’ve personally put a lot of effort in making this part accessible also to machines – e.g. see the SPAR Ontologies. Honestly, this is something very difficult to achieve in an automatic or semi-automatic fashion, and it is not the point of the I4OC, at least not at this stage.
or the content (at least the title and abstract) of the cited source.
Well, when I wrote about citation data in the previous comments I actually meant that other metadata are also included or can be easily derived. For instance, the title is among the information that Crossref returns, in addition to the authors, publication dates, etc. Since these can be considered ‘facts’, they can be released in the public domain without any issue.
I guess this is more tricky for the abstract, since that specific part is actually copyrighted – it is not a fact, it is a creative content written by the authors. It is worth mentioning that this holds for both closed- and open-access publications. In fact, a CC-BY license (usually adopted by open access journals) is not enough for guaranteeing a fully open reuse. Only a CC0 Public Domain Dedication and Waiver permits unrestricted reuse, since it is more permissive that a CC-BB license and is widely adopted for data. The intended goal of I4OC is to push for CC0 adoption.
The citation graph is only useful if you have the content and context; if you have that, you already have the citation graph (i.e., the references section).
I slightly disagree here. The citation graph is useful, period, and can be used for computing the metrics you refer to and for additional things as well (e.g. browsing within a large set of the literature available). Having the content and the context is for sure an added value (which could present issues related to the license, as mentioned before). However, having the content open, e.g. because the publication has been released with a CC-BY license, is not enough to have citation data that are structured, separable, and open, which is the main goal the I4OC wants to reach. The fact that these data are available in Crossref means to have a tool for accessing and querying them as a whole, something that you don’t have if you have to parse publications every time you need these data.
