user4558: I'm toying with the idea of building a tactical training tool. For my idea to work, I need positions that are categorized by motif and difficulty.
A lot of tools seem to have this, and I doubt they're all building up thousands of positions by hand. So there must be databases out there, available for use (free or commercial are both okay), and probably already tagged. Any idea where to start looking?

user2607: This is one, http://dejascacchi.altervista.org/exercises.htm
Thus are from real games.
Also the online chess site, chesstempo.com, has problems with an elo rating (calculated as an accumulated result of the success rate of solving by other players of the same site, and it has rankings too). Also has endings problems. All problems seem to be computer generated (for analysis of games).
Also the now death spaniard magazine, "Ocho x Ocho" (from 80s - 90s) had in each number problems classified by 5 levels (Google "ocho x ocho revista de ajedrez").
The books from Franc Loheac Ammoun, available in several languages, for example http://www.amazon.fr/Testez-vous-aux-%C3%A9checs-Frank-Loh%C3%A9ac-Ammoun/dp/2501014006
or http://www.amazon.com/Compruebe-Nivel-Ajedrez-Desarrolle-Razonamiento/dp/8480192410/ref=sr_1_2?ie=UTF8&qid=1421005140&sr=8-2&keywords=Frank-Loh%C3%A9ac-Ammoun%2F
Put you to solve tactical problems and then calculates your rating.
There are other I forgot, will update it here as I remember...

user4362: This kind of thing isn't done by hand, but by computer programs. It is not too difficult to run some program on a game database and extract all positions suitable for a tactical exercise.
Sorting them by difficulty will be done over time, when statistics accumulate how often they are solved correctly.
Of course there are tactical exercise positions out there, but I don't know any that are already sorted by motif or difficulty. This is a site with 10,000 tactical positions (surely mined by a computer):
http://www.wtharvey.com

4558: <p>I'm toying with the idea of building a tactical training tool. For my idea to work, I need positions that are categorized by motif and difficulty.</p>
<p>A lot of tools seem to have this, and I doubt they're all building up thousands of positions by hand. So there must be databases out there, available for use (free or commercial are both okay), and probably already tagged. Any idea where to start looking?</p>
 2607: <p>This is one, <a href="http://dejascacchi.altervista.org/exercises.htm" rel="nofollow">http://dejascacchi.altervista.org/exercises.htm</a>
Thus are from real games.</p>

<p>Also the online chess site, chesstempo.com, has problems with an elo rating (calculated as an accumulated result of the success rate of solving by other players of the same site, and it has rankings too). Also has endings problems. All problems seem to be computer generated (for analysis of games).</p>

<p>Also the now death spaniard magazine, "Ocho x Ocho" (from 80s - 90s) had in each number problems classified by 5 levels (Google "ocho x ocho revista de ajedrez").</p>

<p>The books from Franc Loheac Ammoun, available in several languages, for example <a href="http://www.amazon.fr/Testez-vous-aux-%C3%A9checs-Frank-Loh%C3%A9ac-Ammoun/dp/2501014006" rel="nofollow">http://www.amazon.fr/Testez-vous-aux-%C3%A9checs-Frank-Loh%C3%A9ac-Ammoun/dp/2501014006</a>
or <a href="http://rads.stackoverflow.com/amzn/click/8480192410" rel="nofollow">http://www.amazon.com/Compruebe-Nivel-Ajedrez-Desarrolle-Razonamiento/dp/8480192410/ref=sr_1_2?ie=UTF8&amp;qid=1421005140&amp;sr=8-2&amp;keywords=Frank-Loh%C3%A9ac-Ammoun%2F</a>
Put you to solve tactical problems and then calculates your rating.</p>

<p>There are other I forgot, will update it here as I remember...</p>
 4362: <p>This kind of thing isn't done by hand, but by computer programs. It is not too difficult to run some program on a game database and extract all positions suitable for a tactical exercise.
Sorting them by difficulty will be done over time, when statistics accumulate how often they are solved correctly.</p>

<p>Of course there are tactical exercise positions out there, but I don't know any that are already sorted by motif or difficulty. This is a site with 10,000 tactical positions (surely mined by a computer):</p>

<p><a href="http://www.wtharvey.com" rel="nofollow">http://www.wtharvey.com</a></p>
