Pollack-inconsistency

  • Authors:
  • Freek Wiedijk

  • Affiliations:
  • Institute for Computing and Information Sciences, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2012

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Abstract

For interactive theorem provers a very desirable property is consistency: it should not be possible to prove false theorems. However, this is not enough: it also should not be possible to think that a theorem that actually is false has been proved. More precisely: the user should be able to know what it is that the interactive theorem prover is proving. To make these issues concrete we introduce the notion of Pollack-consistency. This property is related to a system being able to correctly parse formulas that it printed itself. In current systems it happens regularly that this fails. We argue that a good interactive theorem prover should be Pollack-consistent. We show with examples that many interactive theorem provers currently are not Pollack-consistent. Finally we describe a simple approach for making a system Pollack-consistent, which only consists of a small modification to the printing code of the system.