One standard for on line free calculation

One standard for texts and "dead" formulas now is pdf (Adobe).

We can free download Adobe Reader and open documents (in Internet).

Now Elsevier/Knovel is working on same standard for "live" calculation.

In future we can free download ??? and open documents with "live" formulas: input new data for formulas and see new answer!

I think Mathcad (Express) can be this ???. I would like to have some as Mathcad Reader

PS

Now I am working with one team with this ??? - see please http://tools.knovel.com/ie/Help/contributors.htm