Answers.Body: <p>A dual is an alternate solution, other than the intended one, <em>after the first move</em> of a problem or study. If it happens on the <em>first</em> move, the problem or study is called <em>cooked</em> instead.</p>
  
  <blockquote>
    <p><strong>dual</strong></p>
    
    <p>Ideally, White should have only one move at each juncture that solves a problem. If White has an alternative at any stage other than the first move, this is a <em>dual</em>. A dual is not as serious a flaw as a <em>cook</em>, and in minor lines, duals may be permissible (opinions differ on this point). Some problems make a virtue out of dual avoidance – of two apparently equivalent white moves, only one works.</p>
  </blockquote>
  
  <p>(source: <a href="https://en.wikipedia.org/wiki/Glossary_of_chess_problems#D" rel="noreferrer">Wikipedia</a>)</p>
  
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Answers.Text: Wiki misses a slight point: If Black ignores a threat, this is not seen as a dual...usually. (In olden times, one was less lenient about it.) E.g. Kc8 Rb5 Bg1 - Ka8 Pa7. Black has no defense against Rb8#, so is 1...a5 2.Rxa5 a dual?
Answers.UserDisplayName: Hauke Reddmann
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Answers.Text: That may be what the article means by 'minor lines'?
Answers.UserDisplayName: Glorfindel
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Answers.Text: I'd say the case I describe is a *subset* of 'minor lines'. I'd define a minor line as anything that is not thematic. A dual minor is still a thing you should strive to avoid nowadays, whereas hardly anyone cares about a dual by ignorance.
Answers.UserDisplayName: Hauke Reddmann
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Answers.UserDisplayName: Glorfindel
Body: <p>I’ve read up on Babson tasks, and they mention that all known tasks are not perfect because there are duals. I’m not sure what this means exactly. What precisely is a “dual” in chess problems?</p>
  
Tags: <problems><terminology><composing>
Title: What is a “dual” in chess problems, such as the Babson task?
ThreadText: # What is a “dual” in chess problems, such as the Babson task?
  
  (Asked by: username_0 on 2019-04-17)
  
  I’ve read up on Babson tasks, and they mention that all known tasks are not perfect because there are duals. I’m not sure what this means exactly. What precisely is a “dual” in chess problems?
  
  **Tags:** problems, terminology, composing
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2019-04-17. Score: 7 | Accepted answer
  
  A dual is an alternate solution, other than the intended one, *after the first move* of a problem or study. If it happens on the *first* move, the problem or study is called *cooked* instead.
  
  > **dual**
  >
  > Ideally, White should have only one move at each juncture that solves a problem. If White has an alternative at any stage other than the first move, this is a *dual*. A dual is not as serious a flaw as a *cook*, and in minor lines, duals may be permissible (opinions differ on this point). Some problems make a virtue out of dual avoidance – of two apparently equivalent white moves, only one works.
  
  (source: [Wikipedia](https://en.wikipedia.org/wiki/Glossary_of_chess_problems#D))
  
  > **Comments:**
  > **username_2**: Wiki misses a slight point: If Black ignores a threat, this is not seen as a dual...usually. (In olden times, one was less lenient about it.) E.g. Kc8 Rb5 Bg1 - Ka8 Pa7. Black has no defense against Rb8#, so is 1...a5 2.Rxa5 a dual?  
  > **username_1**: That may be what the article means by 'minor lines'?  
  > **username_2**: I'd say the case I describe is a *subset* of 'minor lines'. I'd define a minor line as anything that is not thematic. A dual minor is still a thing you should strive to avoid nowadays, whereas hardly anyone cares about a dual by ignorance.  
  
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