Perhaps it would be more productive if I give a very specific example. (I'd prefer a general, wikidata-wide policy but it sounds like that isn't going to happen.)
We are working on integrating wikidata with many of the ontologies that are part of the OBO Foundry [1]. These include, for example, the Gene Ontology and the Disease Ontology. Bringing the concepts represented in these ontologies in as items in wikidata makes it possible to author claims that capture knowledge about the relationships between, for example, genes, biological processes, diseases, and drugs. These claims are thus far mostly drawn from associated public databases. They serve to populate infoboxes on Wikipedias and, we hope, will also help foster the growth of new applications that can help to capture more knowledge for re-use by the wikidata community. Importantly, these imports also bind the wikidata community here to the community of biomedical researchers over there. Establishing a coherent pattern for binding the concepts in these ontologies to the corresponding items in wikidata is important for two key reasons:
(1) The ontologies and other linked data resources that use them have a lot of data that is never likely to get into wikidata and vice versa. Establishing clear mappings makes it possible to integrate that knowledge (mostly) automatically. (AKA the whole idea of the semantic web...). The more consistent the pattern of mapping, the more automation is possible.
(2) It is vitally important to the maintainers of these resources to be able to track usage of their work products. The more an ontology that is funded for the purpose of supporting research and knowledge dissemination can show that it is being used, the better the argument to continue its funding. When negotiating the import of knowledge products into a CC0 world, it is important that we can demonstrate that the items will generally remain connected as well as give indications about how they are being used. (Accepting of course that with CC0 there is no guarantee.)
Given that context, would you support the proposal of using the exact match property to bind this specific set of biomedical wikidata items to items defined elsewhere on the semantic web? If not, what would be the best alternative?
-Ben