The correct solution would be to change the behavior of the renderer to look for old versions of templates and data items, but Wikidata wouldn't be pressured to do this until Wikipedia changed the way it renders templates. To pressure Wikipedia into changing the way it renders templates you will need more people that want think this feature is important. The only time I ever look at old versions of articles is when I'm looking at a change from my watchlist or looking for the most recent change that wasn't vandalized if I randomly come across vandalism.
> From: g.m.hagedorn@gmail.com
> Date: Sat, 6 Apr 2013 22:49:24 +0200
> To: wikidata-l@lists.wikimedia.org
> Subject: Re: [Wikidata-l] Page history and properties
>
> > This is great, but the solution I saw (i.e.
> > {{#property:population|current-value=309000000}}) makes the whole
> > Wikidata absolutely useless.
>
> (I asked Luca back about this, and perhaps one point is that the term
> "current" is too easily misunderstood. The point is not that wikidata
> should have such a property, but that the value at the time of saving
> a past version of a wikipedia page is preserved. Perhaps
>
> {{#property:population|value-when-saving-page=309000000}}
>
> would be less easily misunderstood. nothing in Wikidata would be made
> useless by this, it would work exactly like now when calling the
> current page, it would only work differently when calling the
> cite-thiy-version-of-a-page links. And it would allow a wikipedia
> community to structure their work such that Wikipedia editors can
> still curate and see changes to the values.
>
> --------
>
> However, as said above, this is just an example of a solution. It is
> safe, very small processing overhead, small storage overhead and
> scales well to load.
>
> A more elegant solution would clearly be to do two things:
>
> a) when creating a Wikipedia diff on the Wikipedia page version
> history, to either show directly, or link to a Wikidata property diff
> (reduced to the relevant parts as outlined in an earlier mail) in
> addition to the wikitext diff of the page.
>
> Note that it is not necessary to merge all Wikidata versions into the
> Wikipedia version. When comparing two arbitraty Wikipedia page
> version, it is irrelvant whether 1 or multiple Wikidata changes are
> included, all corresponding changes should be shown on request. The
> only necessary item is a single Wikidata indicator (operating like a
> special version line) on top for cases where Wikidata properties are
> changed after the last Wikipedia edit.
>
> b) expand the property function such that for all calls of specific
> (citable) page versions, it retrieves the property rendering at that
> point in time from wikidata.
>
> Gregor
>
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