Answers.Body: <p>Strictly speaking, you're looking at opening <em>practice</em>, not theory. The theory is in books, articles, Chessable courses, et cetera.</p>
  <p>Main lines in opening theory are those where there is some consensus that they are <em>currently</em> the best try for getting a <em>white advantage / managing to equalize as black</em>.</p>
  <p>The difference is that <em>once an equal position is obvious, opening theory ceases to be interested</em>.</p>
  <p>E.g., take a popular line like 1.d4 d5 2.c4 c6 3.Nc3 e6 4.Nf3 Nf6 5.cxd5 exd5.</p>
  <p>Opening theory doesn't really treat this at all -- you get text like &quot;an inferior version of the Queen's Gambit Declined, Exchanged Variation, in which black can easily achieve ...Bf5 and equalize.&quot; Even though it has been played thousands of times and is dangerous: Matthew Sadler in his book on the QGD notes that he kept losing in this line as a young IM. But the knowledge required is <em>strategical</em>, not opening theoretical -- as there is hardly any concrete theory. So strong players play a move like that to just get a game of chess while avoiding too much theory.</p>
  <p>So what is the goal of your tool? Most people who want to learn theory want to learn the <em>best</em> lines as a far as currently known (i.e., opening theory). You are looking at the <em>most played</em> lines.</p>
  <p>IMO memorizing such lines isn't going to be much use as it's all equalish and nobody will follow specific lines much after it, it's just a game of chess.</p>
  <p>(Note: I don't actually play that French line in your question and don't know what theory says about Nce2 -- it might be an important theoretical line. But you can't tell just from the numbers).</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-28T11:49:42.500Z
Answers.LastActivityDate: 2024-09-28T12:23:11.287Z
Answers.LastEditDate: 2024-09-28T12:23:11.287Z
Answers.UserDisplayName: RemcoGerlich
Answers.Body: <p>There is no objective definition of what constitutes a mainline. Even if we went for something like &quot;only the most played move after the line gets a specific name&quot;, you could still have different mainlines depending on what database you use as your sample.</p>
  <p>I'd just try different heuristics for moves that are played often enough to matter until you get a sensible game tree, big enough to cover your needs but small enough to still be manageable.</p>
  <p>For instance after 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Black can choose between 5...a6, 5...Nc6, 5...g6 or 5...e6 leading to the Najdorf, Classical, Dragon and Scheveningen Sicilians respectively, so I guess you'd want to include all four moves. But in the Najdorf White can play both 6.Bg5 or 6.Be3 and I can't see why one would include the Scheveningen but exclude one of those.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-28T18:08:36.080Z
Answers.Text: or 6. Bc4 or 6. Be2
Answers.UserDisplayName: Alexander Woo
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-28T08:12:18.903Z
Answers.LastActivityDate: 2024-09-28T17:07:52.987Z
Answers.LastEditDate: 2024-09-28T17:07:52.987Z
Answers.UserDisplayName: David
Body: <p>I am working on a graph showing <em>all</em> of mainline opening theory until say move 10.</p>
  <p>I’m using an openings database for the moves. Now, sometimes the database looks like</p>
  <p><a href="https://i.sstatic.net/nBlUbIPN.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/nBlUbIPN.jpg" alt="Opening’s database after the Steiniz French Main Line" /></a></p>
  <p>Now, I know that f4 is the mainline. But if 1700 masters have played have played Nce2, <strong>does that mean that it’s a mainline too? How to know when a line is not inportant enough to note (e.g. Qh5)?</strong></p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-09-28T09:02:01.743Z
Comments.Text: Note that "mainline" is also subject to historical changes. Heuristic: if it got a name, it's a mainline (not that this helps much). Have you tried making a graph based on engine evaluation alone? Also, dupe?: https://chess.stackexchange.com/questions/41040/what-makes-an-opening-move-the-mainline?rq=1
Comments.UserDisplayName: Hauke Reddmann
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-09-28T22:20:42.027Z
Comments.Text: I think it is a duplicate @HaukeReddmann
Comments.UserDisplayName: MrChessR
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-09-29T14:58:28.207Z
Comments.Text: IMHO same question, different aspect.
Comments.UserDisplayName: Hauke Reddmann
Tags: <opening><theory>
Title: How to define a mainline theory move?
ThreadText: # How to define a mainline theory move?
  
  (Asked by: username_0 on 2024-09-28)
  
  I am working on a graph showing *all* of mainline opening theory until say move 10.
  
  I’m using an openings database for the moves. Now, sometimes the database looks like
  
  [![Opening’s database after the Steiniz French Main Line](https://i.sstatic.net/nBlUbIPN.jpg)](https://i.sstatic.net/nBlUbIPN.jpg)
  
  Now, I know that f4 is the mainline. But if 1700 masters have played have played Nce2, **does that mean that it’s a mainline too? How to know when a line is not inportant enough to note (e.g. Qh5)?**
  
  **Tags:** opening, theory
  
  > **Comments:**
  > **username_1**: Note that "mainline" is also subject to historical changes. Heuristic: if it got a name, it's a mainline (not that this helps much). Have you tried making a graph based on engine evaluation alone? Also, dupe?: https://chess.stackexchange.com/questions/41040/what-makes-an-opening-move-the-mainline?rq=1  
  > **username_2**: I think it is a duplicate @username_1  
  > **username_1**: IMHO same question, different aspect.  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_3 on 2024-09-28. Score: 1
  
  Strictly speaking, you're looking at opening *practice*, not theory. The theory is in books, articles, Chessable courses, et cetera.
  
  Main lines in opening theory are those where there is some consensus that they are *currently* the best try for getting a *white advantage / managing to equalize as black*.
  
  The difference is that *once an equal position is obvious, opening theory ceases to be interested*.
  
  E.g., take a popular line like 1.d4 d5 2.c4 c6 3.Nc3 e6 4.Nf3 Nf6 5.cxd5 exd5.
  
  Opening theory doesn't really treat this at all -- you get text like "an inferior version of the Queen's Gambit Declined, Exchanged Variation, in which black can easily achieve ...Bf5 and equalize." Even though it has been played thousands of times and is dangerous: Matthew Sadler in his book on the QGD notes that he kept losing in this line as a young IM. But the knowledge required is *strategical*, not opening theoretical -- as there is hardly any concrete theory. So strong players play a move like that to just get a game of chess while avoiding too much theory.
  
  So what is the goal of your tool? Most people who want to learn theory want to learn the *best* lines as a far as currently known (i.e., opening theory). You are looking at the *most played* lines.
  
  IMO memorizing such lines isn't going to be much use as it's all equalish and nobody will follow specific lines much after it, it's just a game of chess.
  
  (Note: I don't actually play that French line in your question and don't know what theory says about Nce2 -- it might be an important theoretical line. But you can't tell just from the numbers).
  
  
  ---
  
  ### Answer by username_4 on 2024-09-28. Score: 1
  
  There is no objective definition of what constitutes a mainline. Even if we went for something like "only the most played move after the line gets a specific name", you could still have different mainlines depending on what database you use as your sample.
  
  I'd just try different heuristics for moves that are played often enough to matter until you get a sensible game tree, big enough to cover your needs but small enough to still be manageable.
  
  For instance after 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Black can choose between 5...a6, 5...Nc6, 5...g6 or 5...e6 leading to the Najdorf, Classical, Dragon and Scheveningen Sicilians respectively, so I guess you'd want to include all four moves. But in the Najdorf White can play both 6.Bg5 or 6.Be3 and I can't see why one would include the Scheveningen but exclude one of those.
  
  > **Comments:**
  > **username_5**: or 6. Bc4 or 6. Be2  
  
  ---
  
  