On
https://meta.wikimedia.org/wiki/Wikidata/Notes/URI_scheme#Proposal_for_Wiki…
I am missing the arguments why Wikidata needs the multitude of URI
forms. The list needs commenting and arguments why
"URIs should be canonical within Wikimedia projects"
is given up.
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(Of lesser importance, I wonder why the internal opaque ID has to be
prefixed by a letter (Q) - why not a simple number?)
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At them moment I believe a choice should be made between:
http://{site}.wikidata.org/wiki/{title} and
http://wikidata.org/title/{site}:{title}
but perhaps the argument why both are needed could be added.
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On the issue of interlanguage/interwiki linking, I believe the
semantics should not be opposite in Wikidata and Wikipedias, see my
comment
https://meta.wikimedia.org/wiki/Talk:Wikidata/Notes/Wiki_links
Gregor