A sort key in MoStacks defines a sort order for cards of a certain background. In simple terms, the cards will be sorted alphabetically according to the "key strings" built based on the sort key definition. You find details in chapter Sorting.
However, when one looks closer, this sorting or "bringing into order" has a surprising number of facets and problems.
One important point is that sort orders are dependent on the so-called locale: Even among the countries that use the Latin alphabet, there are slightly different conventions for sorting in use. Just one example: The Germans sort their "Umlaut" characters ä, ö und ü together with the corresponding base letters a, o and u, whereas people in Sweden take the Umlauts as letters in their own right and sort them, maybe somewhat surprisingly, after Z!
If you configure your Windows PC or your smartphone for another country (in Windows by specifying a different country in the "Control Panel"), all applications dealing with sorting are expected to adjust accordingly. Likewise on a Symbian smartphone.
This results in a fundamental problem for MoStacks (and databases in general): If you change the locale, you may invalidate the sort order of the cards, i.e. according to the new locale, the cards are not correctly sorted anymore. Because of technical reasons, MoStacks has no other way to solve this problem than by re-sorting the cards.
When MoStacks loads a stack, it checks whether everything that should be sorted is still sorted, according to the rules that are valid at that given moment on your Windows PC or your Symbian smartphone, and if there is any deviation, adjusts the card order to "restore order" and informs you about doing so.
Because of this, it's best if your PC and your phone have the same locale setting!
Thanks to the capabilities of the underlying operating systems (Microsoft Windows and Symbian) MoStacks supports Unicode. This is why we are not only talking about how to sort a few dozens letters and accented/umlauted variants from the Latin alphabet, but about sorting of many thousands of characters, with Chinese, Japanese, Indian, Hebrew, Arabic and many more among them.
In more special cases, concerning e.g. the exact treatment of punctuation or strings that only differ in case, there may be small sort order differences between Windows and Symbian even if the two are correctly configured for the same locale, and this may already trigger a warning about "sort order corrections".
Anyway, MoStacks does not sort itself, but uses services from the underlying operating system to do so, and therefore MoStacks has really not much to say about the resulting sort orders. It can only detect when something that should be sorted isn't, and act accordingly.