Editing Chess problem (section)

==Beauty in chess problems==
[[Image:Pawn2knight.gif|frame|right|Black mating on move 5 by promoting to knight]]
The role of [[Chess aesthetics|aesthetic evaluation]] in the appreciation of chess problems is very significant, and indeed most composers and solvers consider such compositions to be an art form. [[Vladimir Nabokov]] wrote about the "originality, invention, conciseness, harmony, complexity, and splendid insincerity" of creating chess problems and spent considerable time doing so. There are no official standards by which to distinguish a beautiful problem from a poor one and such judgments can vary from individual to individual as well as from generation to generation.  Such variation is to be expected when it comes to aesthetic appraisal.  Nevertheless, modern taste generally recognises the following elements to be important in the aesthetic evaluation of a problem:

*The problem position must be legal. That is to say, the diagram must be reachable by legal moves beginning with the initial game array. It is not considered a defect if the diagram can only be reached via a game containing what over-the-board players would consider gross blunders.
*The first move of the problem's solution (the ''key move'' or ''key'') must be unique. A problem which has two keys is said to be ''cooked'' and is judged to be ''unsound'' or defective. (Exceptions are problems which are composed to have more than one solution which are thematically related to one another in some way; this type of problem is particularly common in helpmates.)
*Ideally, in directmates, there should be a unique White move after {{em|each}} Black move. A choice of White moves (other than the key) is a ''dual''. Duals are often tolerated if the problem is strong in other regards and if the duals occur in lines of play that are subsidiary to the main theme.
*The solution should illustrate a theme or themes, rather than emerging from disjointed calculation. Many of the more common themes have been given names by problemists (see [[chess problem terminology]] for a list).
*The key move of the solution should not be obvious. Obvious moves such as checks, captures, and (in directmates) moves which restrict the movement of the black king make for bad keys. Keys which deprive the black king of some squares to which it could initially move (''flight squares''), but at the same time make available an equal or greater number of flight squares are acceptable. Key moves which prevent the enemy from playing a checking move are also undesirable, particularly in cases where there is no mate provided after the checking move.  In general, the weaker (in terms of ordinary over-the-board play) the key move is the less obvious it will be, and hence the more highly prized it will be.
*There should be no [[promotion (chess)|promoted]] pawns in the initial position. For example, if White has three knights, one of them must clearly have been promoted; the same is true of two {{chessgloss|light-square bishops}}. There are more subtle cases: if f1 is empty, a white bishop stands on b5 and there are white pawns on e2 and g2, then the bishop must be a promoted pawn (there is no way the original bishop could have gotten past those unmoved pawns). A piece such as this, which does not leave a player with pieces additional to those at the start of a game, but which nonetheless must have been promoted, is called ''obtrusive''. The presence of obtrusive units constitutes a smaller flaw than the presence of more obviously promoted units. 
*The problem should be economical.<ref>Iqbal, A. (2008). Evaluation of Economy in a Zero-sum Perfect Information Game, The Computer Journal, Oxford University Press, Vol. 51, No. 4, pp. 408–418, {{doi|10.1093/comjnl/bxm060}}. Online ISSN 1460-2067, Print ISSN 0010-4620. http://comjnl.oxfordjournals.org/content/51/4/408.abstract {{Webarchive|url=https://web.archive.org/web/20160608122007/http://comjnl.oxfordjournals.org/content/51/4/408.abstract |date=2016-06-08 }}</ref>  There are several facets to this desideratum.  For one thing, every piece on the board should serve a purpose, either to enable the actual solution, or to exclude alternative solutions. Extra units should not be added to create "red herrings" (this is called ''dressing the board''), except in rare cases where this is part of the theme. If the theme can be shown with fewer total units, it should be.  For another, the problem should not employ more moves than is needed to exhibit the particular theme(s) at its heart; if the theme can be shown in fewer moves, it should be.