I sent this message into wikitech-l; I presume it's better to share content with wikisource people too.

As you know, wikisource needs robust, well-defined data, and there's a

strict, deep relationship between wikisource and Commons since Commons hosts images of books, in .djvu or .pdf files. Commons shares both images and contents fo information page of images, so that any wiki project can visualize a view-only "pseudo-page" accessing to a local page named as the file name into Commons.

Working into self-made data semantization into it.wikisouce using a lot of creative tricks, we discovered that it's hard/almost impossible to read by AJAX calls the contents of pages of other projects since well-known same origin policy, but that File: local pages are considered as coming from "same origin" so that they can be read as any other local page, and this AJAX call asking for the content of i.e. File:Die_Judenfrage_in_Deutchland_1936.djvu:

html=$.ajax({url:" http://wikisource.org/wiki/File:Die_Judenfrage_in_Deutchland_1936.djvu ",async:false}).responseText;

gives back the html text of local File: view-only page, and this means that any data stored into information page into Commons is freely accessible by a javascript script and can easily used locally. In particular, data stored into information and/or (much better) Book and Creator templates can be retrieved and parsed

Has this been described/used before? It seems a plain, simple way to share and disseminate good, consistent metadata into any project; and this runs from today, without any change on current wiki software.

If you like, I'm sharing a practical test use of this trick into wikisource.org too, you can import User:Alex brollo/Library.js and a lot of smallo, original scripts will be loaded; click on "metadata" botton from any page connected to a File: page ( namespaces Index, Page) and you'll see a result coming from such an AJAX call.

Alex brollo, from it.wikisource