Answers.Body: <p>Your question has two different nuances, that is, how to classify an opening and how to classify a game.</p>
  
  <p>The Encyclopedia of Chess Openings' only aim is to classify the first moves of a chess game, it does not concern itself with how the game develops nor further transpositions. Even if a widely known position is reached after an unorthodox choice of moves, the ECO will classify the opening according to these first moves. A comprehensive list can be found both in <a href="https://www.365chess.com/eco.php" rel="nofollow noreferrer">365Chess</a> and <a href="https://en.wikipedia.org/wiki/List_of_chess_openings" rel="nofollow noreferrer">Wikipedia</a>, the first provides easy access to the variation in question and the second provides the name and some contextualization for the variation.</p>
  
  <p>While the ECO has not an analogous encyclopedia for complete games, the widespread and common way of treating them in the literature is to find the last instance of a known tabiya and consider the game under its umbrella. This ignores the concrete opening, which is often useful since the game may be a relevant addition to the theory on that position, and thus the particular move order leading to it is irrelevant.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-10-10T16:11:28.887Z
Answers.LastActivityDate: 2017-10-10T16:11:28.887Z
Answers.UserDisplayName: Pablo S. Ocal
Body: <p>Positions in an opening can often be reached in a variety of (meaningful) ways, i.e. by <em>transpositions</em>.</p>
  
  <p>When classifying chess games (e.g. in databases or books) by , are there rules or other guidelines which of these transpositions to pick?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-09T21:30:32.423Z
Comments.Text: In databases, it is not so much of a problem. In books, the usual way is to refer to a given position by the name of the opening by which it has been reached first (and most often) in high-level practice. For instance, 1.e4 c5 2.c3 e6 3.d4 d5 4.e5 is "transposing into the French defense, advanced variation" because the position has been reached earlier and much more often among grandmasters via a French than via an Alapin Sicilian.
Comments.UserDisplayName: Evargalo
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-10-10T11:53:39.250Z
Comments.Text: Go _backwards_ through the game, then use the name of the first named position you reach.
Comments.UserDisplayName: RemcoGerlich
Tags: <opening><transpositions>
Title: Opening classification and transpositions
ThreadText: # Opening classification and transpositions
  
  (Asked by: username_0 on 2017-10-09)
  
  Positions in an opening can often be reached in a variety of (meaningful) ways, i.e. by *transpositions*.
  
  When classifying chess games (e.g. in databases or books) by , are there rules or other guidelines which of these transpositions to pick?
  
  **Tags:** opening, transpositions
  
  > **Comments:**
  > **username_1**: In databases, it is not so much of a problem. In books, the usual way is to refer to a given position by the name of the opening by which it has been reached first (and most often) in high-level practice. For instance, 1.e4 c5 2.c3 e6 3.d4 d5 4.e5 is "transposing into the French defense, advanced variation" because the position has been reached earlier and much more often among grandmasters via a French than via an Alapin Sicilian.  
  > **username_2**: Go _backwards_ through the game, then use the name of the first named position you reach.  
  
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  ## 1 answers
  
  ### Answer by username_3 on 2017-10-10. Score: 1 | Accepted answer
  
  Your question has two different nuances, that is, how to classify an opening and how to classify a game.
  
  The Encyclopedia of Chess Openings' only aim is to classify the first moves of a chess game, it does not concern itself with how the game develops nor further transpositions. Even if a widely known position is reached after an unorthodox choice of moves, the ECO will classify the opening according to these first moves. A comprehensive list can be found both in [365Chess](https://www.365chess.com/eco.php) and [Wikipedia](https://en.wikipedia.org/wiki/List_of_chess_openings), the first provides easy access to the variation in question and the second provides the name and some contextualization for the variation.
  
  While the ECO has not an analogous encyclopedia for complete games, the widespread and common way of treating them in the literature is to find the last instance of a known tabiya and consider the game under its umbrella. This ignores the concrete opening, which is often useful since the game may be a relevant addition to the theory on that position, and thus the particular move order leading to it is irrelevant.
  
  
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