The string is interpreted by the math extension in the same way as the Math extension interprets the text between the <math /> tags.
There is an API to extract identifiers and the packages required to render the input with regular latex from here:
http://api.formulasearchengine.com/v1/?doc
or also
https://en.wikipedia.org/api/rest_v1/?doc#!/Math/post_media_math_check_type
(The wikipedia endpoint has been opened to the public just moments ago)
In the future, we are planning to provide additional semantics from there.
If you have additional questions, please contact me directly, since I'm not a member on the list.
Moritz

On Tue, Feb 2, 2016 at 8:53 AM, Lydia Pintscher <Lydia.Pintscher@wikimedia.de> wrote:
On Mon, Feb 1, 2016 at 8:44 PM Markus Krötzsch <markus@semantic-mediawiki.org> wrote:
On 01.02.2016 17:14, Lydia Pintscher wrote:
> Hey folks :)
>
> I just sat down with Katie to plan the next important feature
> deployments that are coming up this month. Here is the plan:
> * new datatype for mathematical expressions: We'll get it live on
> test.wikidata.org <http://test.wikidata.org> tomorrow and then bring it
> to wikidata.org <http://wikidata.org> on the 9th

Documentation? What will downstream users like us need to do to support
this? How is this mapped to JSON? How is this mapped to RDF?

It is a string representing markup for the Math extension. You can already test it here: http://wikidata.beta.wmflabs.org/wiki/Q117940. See also https://en.wikipedia.org/wiki/Help:Displaying_a_formula. Maybe Moritz wants to say  bit more as his students created the datatype.

Cheers
Lydia
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